JPH037725B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new method for manufacturing a non-oriented electrical steel sheet that fully develops the 110,001 orientation in a process based on rolling and annealing, and satisfies both improvement in magnetic flux density and reduction in iron loss. For magnetic steel sheets, it is already well known that steel sheets with a high degree of integration in 110,001 directions are preferable in order to improve the magnetic flux density regardless of whether the magnetic flux is oriented or non-directional. Non-oriented electrical steel sheets are made by hot rolling ultra-low carbon steel or low carbon aluminum killed steel with Si and Al added as necessary, and then cold rolling once or twice with intermediate annealing in between. After being made into a cold-rolled steel sheet of product thickness, it is manufactured by final annealing and, if necessary, temper rolling. In this conventional method, a combination of cold rolling and annealing is performed twice.
Because the process is repeated several times, energy consumption in the manufacturing process is also large. On the other hand, a high accumulation of 100,001 could not be obtained with a single combination of cold rolling and annealing. On the other hand, if the present invention is applied, it is possible to sufficiently increase the concentration of 110,001 in a single treatment combining rolling and annealing, and a non-oriented electrical steel sheet with high magnetic flux density and low hysteresis loss can be obtained. can be obtained. Accordingly, the present invention produces an electrical steel sheet having a 110,001 texture in the main orientation, but such a steel sheet is also conventionally classified as a non-oriented electrical steel sheet. That is, in the present invention, the solid solution (C+N) is 10 ppm or more.
Low carbon steel with a carbon content of 200 ppm or less is rolled at a temperature range of 200 to 500°C with a reduction rate of 20% or more and 80% or less, and then recrystallized annealing is performed to develop the 110,001 orientation component of the texture. The main point is a method for manufacturing non-oriented electrical steel sheets, which is characterized by the following. The contents of the present invention will be explained in detail below. The present invention produces severe dynamic strain aging in the rolling stage prior to annealing, and utilizes the resulting special processed structure to improve the texture after annealing.
The aim is to increase the 10,001 direction component. Dynamic strain aging is strain aging during processing that occurs due to the interaction between dislocations that move during processing and solid solution C and N in the steel. According to the results of detailed research related to the present invention, when severe dynamic strain aging occurs during rolling, band-shaped regions with particularly large processing strains (hereinafter referred to as deformation bands) are formed within grains, and during annealing, these band-shaped regions are formed. 1 in the deformation zone
10,001 recrystallization nuclei are preferentially formed and contribute to an increase in the 110,001 orientation component in the texture after annealing. In order to produce such dynamic strain aging, the low carbon steel material must first have a sufficient amount of solid solution (C+
must contain N), and the solid solution (C+N) measured by internal friction method etc. at the stage of warm rolling.
must be 10ppm or more. Solid solution (C
+N) is less than 10 ppm, the degree of dynamic strain aging is so small that the effects of the present invention cannot be expected. Further, in the present invention, the larger the amount of solid solution (C+N), the more effective it is, but the upper limit is 200 ppm from the solid solubility limit of (C+N) in the ferrite phase, and more preferably in the range of 50 to 150 ppm. Next is the rolling temperature. At temperatures below 200℃, the diffusion of C and N atoms in the steel is slow, and the time required for C and N atoms to diffuse and move toward dislocations is too long, resulting in dynamic strain aging. It doesn't happen enough. Also
In the temperature range over 500℃, C and N diffuse quickly enough to
N atoms can easily reach dislocations, but dislocations and C,
The interaction with N atoms is weak, and dynamic strain aging disappears. Therefore, the rolling temperature must be in the range of 200 to 500°C, that is, in the range of warm rolling (hereinafter referred to as hot rolling). Further, if the reduction ratio during rolling is less than 20%, the amount of multiplication of dislocations during rolling is small, and therefore dynamic strain aging does not occur violently and is not effective. For this reason, the rolling reduction ratio must be 20% or more. When the reduction rate during rolling exceeds 80%, the dislocation density becomes extremely high.
On the contrary, since the deformation becomes uniform and no deformation band exists anymore, the effects of the present invention cannot be expected in this case. Among these, the preferred rolling reduction ratio during rolling is in the range of 50 to 75%. Since the effects of the present invention are manifested by recrystallization after rolling, it is necessary to perform recrystallization annealing under conditions that cause recrystallization after rolling under the above conditions. That is, continuous annealing (for example, 700° C. to 800° C.×5 minutes) recrystallization annealing, which is normally employed in the production of non-oriented electrical steel sheets, is performed to develop the 110,001 orientation component. The material steel used in carrying out the present invention is 10ppm.
It is sufficient to contain the above solid solution (C+N), and there is no need to add other special elements. However, due to the need to improve electromagnetic properties such as iron loss, Al and Si are commonly added.
Even if a large amount of alloying elements such as C +
N) is possible, and the effect of the present invention appears. That is, when Al is added, the solid solution N becomes N
Since the atoms are fixed as AlN, it decreases or ceases to exist, but it is easy to increase the solid solution C to 10 ppm or more. Furthermore, as is well known, when a large amount of Si is added (up to about several percent), the amount of solid solution (C+N) does not change significantly. The temperature under the conditions specified in the present invention is effective even if it is carried out in combination with other rolling, that is, hot rolling-hot rolling, hot rolling-cold rolling, or hot rolling-hot rolling-cold rolling. In this case, it is desirable that the rolling reduction in cold rolling is equal to or lower than that in hot rolling. Example 1 1200 vacuum melted steels with different C and N contents
℃, hot-rolled to a thickness of 2.0 mm at a finishing temperature of 950℃, and air-cooled. Table 1 shows the chemical composition of these samples and the amount of solid solution (C+N) evaluated by the internal friction method.

【table】

[Table] Other elements in all samples are as follows. Si≦0.01%, Mn=0.01%, P=0.002%, S=
0.004%, Al=0.002%, balance Fe. These samples were heated to room temperature at a reduction rate of 10 to 80%.
After rolling at a temperature of 700°C and recrystallization annealing at 700°C for 5 minutes, an X-ray pole figure was created for each sample. The X-ray reflection intensity ratio (based on the sample) was determined. This is because it is well known that the directional component intensity ratio of 110,001 is closely related to the magnetic properties in the rolling direction, and generally, those with a high directional component intensity ratio of 110,001 have good magnetic properties. It is. This can also be seen from Figures 3 and 4, which will be described later.
It can be seen that when the 110,001 intensity ratio is high, the saturation magnetic flux density and iron loss are improved. The relationship between this 110,001 intensity ratio, components, and process conditions is shown in FIGS. 1 and 2. Figure 1 shows one of the samples manufactured under the various conditions mentioned above.
The measurement results of the 10,001 orientation component strength ratio are summarized and the relationship between the fixed (C+N) amount of the hot rolled sheet before hot rolling and the random strength ratio of the 110,001 orientation component after annealing is shown. FIG. 1 shows the results of hot rolling at a rolling temperature of 370° C., and the horizontal axis is the amount of solid solution (C+N), which corresponds to the solid solution (C+N) in Table 1. As can be seen from Fig. 1, when a sample with a solid solution (C+N) of 10 ppm or more, which is within the scope of the present invention, is hot rolled (rolling temperature 370°C) at a reduction rate of 20% or more, 110, 001 intensity ratio becomes significantly higher.
(In the figure, A shows a rolling reduction rate of 70%, B shows a rolling reduction rate of 30%, and C shows a rolling reduction rate of 10%.) On the other hand, in Figure 2, the measurement results are arranged in the same way as in Figure 1, and the rolling reduction rate is 50%. This figure shows the relationship between the rolling temperature and the random strength ratio of the 110,001 orientation component after annealing in the case of 110,001% of the rolling temperature.
It is shown that this contributes to a significant increase in the 0,001 intensity ratio. (a in the figure; sample No. 6 of the present invention material,
b: Comparative material sample No. 1 is shown. ) Conventional process materials, that is, solid solution (C + N) is 10ppm
When rolling is performed at room temperature in a state where the magnetic properties are less than 1, the 110,001 intensity ratio, which is closely related to magnetic properties, becomes approximately 1, which is a lower value than in the case of the present invention. On the other hand, the 110,001 strength ratio of currently manufactured non-oriented electrical steel sheets is usually 0.5 or less after undergoing the hot rolling-cold rolling-final annealing process. Therefore, it is possible not only to improve the magnetic properties of the product of the present invention, but also to omit steps in the current process. Example 2 Samples No. 2 and No. 7 in Table 1 were used at room temperature to
After rolling 75% of each sample separately at each temperature of 700℃ to obtain a plate thickness of 0.5mm, recrystallization was completed by annealing at 700℃ for 5 minutes, and the electromagnetic properties of each sample in the rolling direction were measured. The results are shown in FIGS. 3 and 4. As is clear from the figure, the invention material a (sample No. 7)
When rolled under the conditions of the present invention (200 to 500°C) (reduction ratio 75%, plate thickness 0.5 mm), comparative material B (sample No.
Compared to 2), high magnetic flux density and low iron loss values were simultaneously obtained in the rolling direction, and the electromagnetic properties were significantly improved. As described above, the present invention exhibits the effect of significantly improving magnetic properties simply by adjusting the amount of solid solution (C+N) in the steel before warm rolling and adopting an appropriate rolling temperature. Example 3 C: 0.050%, Si: 2.90%, Mn: 0.086%, S:
Steel with a chemical composition of 0.025%, Sol.Al: 0.027%, and N: 0.0071% was melted, heated to 1300℃, hot rolled to a thickness of 2.0mm at a finishing temperature of 970℃, and then heated to 400℃ during air cooling. ℃ and room temperature, 75% of each was rolled separately to give a thickness of 0.5 mm. Thereafter, recrystallization was completed by annealing at 800°C for 5 minutes, and the electromagnetic properties in the rolling direction were measured. The results are shown in Table 2. However, the solid solution (C+N) immediately before 75% rolling was 83 ppm immediately before rolling at 400° C. and 72 ppm immediately before rolling at room temperature, as measured by the internal friction method. As is clear from the table, the material of the present invention simultaneously achieves high magnetic flux density and low core loss, and by applying the present invention, the electromagnetic properties can be significantly improved.

[Table] As can be seen from this example, the method of the present invention is effective even when Si is contained, and unlike Examples 1 and 2, since Si is added, the iron loss W _15/50 is significantly reduced. It is declining.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the amount of solid solution (C+N) in the hot rolled sheet and the random strength ratio of the 110,001 orientation component after annealing, and Figure 2 shows the relationship between the rolling temperature and the 110,001 orientation component after annealing.
Relationship diagram with random intensity ratio of 01 azimuth component, 3rd
The figure is a diagram showing the relationship between rolling temperature and magnetic flux density, and FIG. 4 is a diagram showing the relationship between rolling temperature and iron loss value.

Claims (1)

[Claims] 1 Low carbon steel with a solid solution (C+N) of 10 ppm or more and 200 ppm or less in a temperature range of 200 to 500℃
Rolling is performed at a rolling reduction of 20% or more and 80% or less, and then recrystallization annealing is performed to improve the texture of 110,001
A method for manufacturing non-oriented electrical steel sheets using warm rolling, which is characterized by developing directional components.