JPS5830925B2 - Manufacturing method for low-grade electrical steel sheets - Google Patents

Description

[Detailed Description of the Invention] The present invention is a low grade electromagnetic steel sheet (
The present invention relates to a method of manufacturing a magnetic permeability μm 5/60 (approximately 2000 to 3000).

Low-grade electrical steel sheets undergo the same processes as ordinary cold-rolled steel sheets: hot rolling, pickling, cold rolling, electroplating, box annealing, temper rolling,
After passing through the inspection and trimming steps, the customer punches the product into a predetermined size and shape, and then performs a strain relief annealing process (SRA process) for the purpose of removing strain and improving magnetism.

However, in conventional manufacturing methods, the components in the steel are adjusted to improve magnetism.

In other words, carbon reduction to reduce iron loss, decarburization in SRA treatment, addition of Si and Mn, and P to improve punchability.
We are also adding .

On the other hand, low SiO is better for improving magnetic permeability, but low S
Since iron loss increases when converting to i, not only is there a limit to the balance between iron loss and magnetic permeability, but fine adjustment of components unnecessarily promotes small lots and multi-product production, which is a prerequisite for efficient production. This is a major obstacle to increasing furnace size and continuous casting.

The purpose of the present invention is to solve the problems in the conventional manufacturing method, and to achieve efficient production and quality (magnetism, shape, , surface defects) and further reduce costs by reducing the number of alloying elements.

By the way, as a result of intensive research by the present inventors in order to solve the problems in the conventional method described above, the present inventors found that Si: 0.02 to 2.
It has been found that continuous annealing of a low-carbon cold-rolled steel sheet containing 0.0 yen, P: 0.05 to 0.15, and the balance being iron significantly improves the magnetic permeability and improves the punchability at the same time.

That is, as shown in the later examples, when the <Si content is the same, continuous annealing significantly improves the magnetic permeability compared to box annealing.

On the other hand, when the Si content is the same, there is almost no difference in iron loss between continuous annealing and box annealing.

Therefore, according to continuous annealing, the magnetic permeability is good even if the Si content of the cold rolled steel sheet is high, and on the other hand, the iron loss is lower as the Si content is higher. It was recognized that steel plates could be manufactured.

Furthermore, the advantage of applying continuous annealing is that continuously annealed cold-rolled steel sheets are harder than box-annealed cold-rolled steel sheets. This means that it can be adjusted as desired.

Conventionally, the amount of P added has been controlled in order to impart and adjust punchability to this type of electrical steel sheet, but such component adjustment complicates steelmaking operations and makes efficient production difficult. However, continuous annealing has the advantage that it is no longer necessary to adjust the punchability by adjusting the components as in the past.

The present invention was constructed based on the above-mentioned knowledge, and its gist is as follows.

Si: 0.02-2.0%, P: 0.05-0.15%
1. A method for producing a low-grade electrical steel sheet, which comprises continuously annealing a low-carbon cold-rolled steel sheet containing the following at a temperature above the recrystallization temperature and below the A3 transformation point, and then temper-rolling it with rolls having a diameter of 100 to 500 mm.

The reason for limiting the chemical composition of the cold rolled steel sheet according to the present invention will be explained.

If Si is less than 0.02%, iron loss will be excessive, so 0.0
The lower limit is 2%, and the upper limit is 2% to ensure high magnetic permeability.
．． It was set to 0%.

The lower limit of P was set at 0.05% from the viewpoint of ensuring strength, and the upper limit was set at 0.15% to prevent excessive strength.

Note that the C content may be the same as that of ordinary low carbon steel, and is not particularly limited, but is preferably 0.07% or less.

Continuous annealing of the present invention is performed in a temperature range from the recrystallization temperature to the A3 transformation point.

The skin pass rolling after continuous annealing is carried out to adjust the punchability by adjusting the rolling reduction ratio, which is preferably in the range of 2 to 7%.

If the thickness is less than 2, the punching method will not be improved, and if it exceeds 7, it will not be too hard and cracks will easily occur during punching.

Next, the effects of the method of the present invention will be explained.

The effect of improving magnetism according to the present invention is shown in FIGS. 1a and 1b.

Figure 1 a shows the iron loss of cold rolled steel sheets obtained by the method of the present invention (○, △), the open coil annealing method (・, M), and the box annealing method (■, A). It also shows magnetic permeability.

As is clear from this figure, according to the method of the present invention, it is possible to significantly improve the magnetic permeability while keeping the iron loss at approximately the same level as in the case of the conventional manufacturing method.

Furthermore, according to the method of the present invention, the punchability can be improved without having to deal with it by increasing the amount of P or other components in the steel (see FIG. 5) as in the past.

The composition of each village in Figure 5 is as follows.

Low [P] material is C: 0.06%, Si: 0.1%, Mn
: 0.44%.

P: 0.07 high, S: 0.019 tai, high [P] material is C:
0.06%, Si: 0.1%, Mn: 0.48%
, P: 0, 127%, S: 0.020%, low [P] material according to the present invention has C: 0.06%, Si: 0.1%, Mn: 0
．． 48 excellent, P: 0.05%, S: 0.016 excellent.

In other words, what is required for the performance of low-grade electrical steel sheets is that they have good punchability at the customer's end, that is, that they are easy to shear and that beautiful sheared surfaces with no burrs can be obtained.
Continuous annealing according to the present invention improves punching properties, and furthermore, adjusting the rolling reduction during temper rolling allows for proper punching properties, thereby reducing manufacturing costs.

FIG. 2 shows the relationship between the pressure-adjusting reduction rate and JHRB, and it can be seen that material quality adjustment by the pressure-adjusting reduction rate is convenient.

In the present invention, 100 to 500w is used in temper rolling.
It is recommended to use small diameter rolls of nφ to save energy such as electricity costs and to reduce the scale of the temper rolling mill.

The reason why the roll diameter is set in the range of 100 to 500 rrtIn is as follows.

The required rolling reduction rate in temper rolling, which is necessary to obtain the optimum crystal grains in SRA processing, increases rapidly when the roll diameter exceeds 500 ranφ, and at the same time, the power required to obtain the same rolling reduction rate increases significantly. The upper limit of the roll diameter is 5 because the synergistic effect of
007ft! ILφ is preferred.

The smaller the roll diameter is, the lower the necessary pressure regulating reduction rate is, reducing the equipment scale and running costs. However, if the roll diameter is less than 100 mm, there will be life problems due to roll wear and problems with formability. Therefore, the lower limit was set to 100 mmφ.

What influences the magnetism is the work roll diameter, and the type of rolling mill may be any type such as a 4-fold rolling mill, a 6-fold rolling mill, a Sendzimer rolling mill, etc., and is not limited to any particular type.

In order to properly grow the crystal grains required to minimize iron loss in the SRA process at the customer, conventional temper rolling mills that use roll diameters of about 500 to 600 tranφ require a wet rolling speed of 5. A rolling reduction ratio of ~7% is required, whereas for a small diameter roll of about 30ONrLφ, the optimal rolling reduction ratio is 3 to 4%.

FIG. 3 is a schematic view of the microscopic structure of the grains after the SRA treatment and the pressure adjustment reduction ratio according to the roll diameter, and the magnification is 100 times.

The steel composition of the material shown in Fig. 3 is C:0.05,
Si: 0.16 poly Mn: 0.40%, P: 0.10%
, S: 0.010%, and the SRA processing conditions are 79
0°C x 1 hour.

As can be seen from Figure 3, in order to obtain a crystal grain size of 200 to 300μ that minimizes iron loss, a large diameter roll of 560mm was used.
In the case of φ, the pressure adjustment reduction ratio of 4 is insufficient, whereas
In the case of a small diameter roll of 300 rranφ, 2.4% is sufficient.

i.e. 100 to 5 according to a preferred embodiment of the invention.
By using a small diameter roll of 00rrrmφ for temper rolling and reducing the regulating reduction ratio, it is possible to save energy such as electric power, and at the same time, it is possible to reduce the size of the temper rolling mill.

Next, an example of an apparatus for carrying out the present invention is shown in FIG.

In the figure, 1 is a rewind reel, 2 is front equipment such as electrolysis,
3 is an entrance looper, 4 is a continuous annealing furnace, 5 is an exit looper, 6 is a temper rolling mill, 7 is a trimming slit section, 8 is an inspection division section, 9 is an oiler, and 10 is a take-up reel.

The effects of the present invention will be specifically explained.

Table 1 below shows the magnetism of two types of cold-rolled steel sheets having the same chemical composition, one by continuous annealing according to the present invention and the other by conventional box annealing.

From Table 1 above, if the chemical composition is the same, the magnetic permeability of the present invention can be improved more than that of box annealing. Then, the Si content is 0.052
%, but with the method of the present invention, it is possible to increase the Si content to 0.209%, and it can be seen that the iron loss can be significantly reduced by that amount.

Next, the influence of the roll diameter of the pressure regulating roll on the magnetism of the electrical steel sheet will be shown by examples.

Example: Cold-rolled steel plate with the composition shown in Table 2 (thickness: 0.5 mm)
Table 3 shows the results of continuous annealing at 600°C for 40 seconds to give a pressure-adjusted elongation rate of 2.5.

As mentioned above, with a small diameter roll, sufficiently good magnetism was obtained even with a pressure-adjusted elongation rate of 2.5 factors.

[Brief explanation of drawings]

Figures 1a and b show the effect of improving magnetism by continuous annealing using the conventional method (
Figure 1 a shows a comparison of iron loss, Figure 1 shows a comparison of magnetic permeability, and Figure 2 shows a comparison between the pressure regulating reduction ratio and JHRB. Figure 3 is a schematic diagram of the metallographic structure showing the effect of temper rolling roll diameter on grain growth after SRA treatment; Figure 4 is a diagram showing an example of an apparatus for carrying out the method of the present invention; FIG. 5 is a diagram showing a comparison of punchability between a steel plate produced by the method of the present invention and a steel plate produced by the conventional method. 1: Rewinding reel, 2: Front equipment, 3: Entry side looper,
4: Continuous annealing furnace, 5: Output side looper, 6: Temper rolling mill,
7: Trimming slit section, 8: Inspection division section, 9: Oiler, 10: Winding reel.

Claims (1)

[Claims] ISi: 0.02-2.0 excellent, P: 0.05-0.15
1. A method for producing a low-grade electrical steel sheet, which comprises continuously annealing a low-carbon cold-rolled steel sheet containing iron at a temperature of not less than a recrystallization temperature and not more than an A3 transformation point, and then skin-pass rolling with rolls having a diameter of 100 to 500 mm.