JP2503112B2 - Manufacturing method of good electromagnetic plate - 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 for manufacturing a good electromagnetic thick plate which has good machinability and excellent magnetic characteristics in a medium magnetic field.

[0002]

2. Description of the Related Art In recent years, along with the progress of elementary particle research and medical equipment, which are the most advanced science and technology, a device using magnetism for a large structure is used, and its performance is required to be improved. In addition to the high saturation magnetic flux density, the magnetic pole material for the particle accelerator and the return yoke material used under the DC magnetizing condition have 5 Oe (400 A /
Although a high magnetic flux density in a medium magnetic field near m) is required, good machinability during processing is also required.

As electromagnetic steel sheets having excellent magnetic flux density, it is well known that many materials such as silicon steel sheets and electromagnetic soft iron sheets have been provided in the field of thin sheets. But,
When used as a structural member, there are problems in assembly processing and strength, and it becomes necessary to use thick steel plates. Until now, electromagnetic plates have been manufactured with pure iron-based components. For example, JP-A-60-96749 is known. However, with the recent increase in the size of the device and the improvement in the capability thereof, the magnetic property is further excellent, especially in the medium magnetic field, for example, 5 Oe
There is a strong demand for the development of steel materials with high magnetic flux density near (400 A / m). Conventionally, a high magnetic flux density of a medium magnetic field near 5 Oe has not been stably obtained.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, and to provide a method for manufacturing a good electromagnetic thick plate which has good machinability and excellent magnetic characteristics in a medium magnetic field. is there.

[0005]

The gist of the present invention is as follows. (1) Weight%, C: 0.01% or less, Si: 0.0
2% or less, Mn: 0.20% or less, P: 0.02 to 0.
20%, S: 0.010% or less, Al: 0.040% or less, N: 0.004% or less, O: 0.005% or less,
H: 0.0002% or less, with the balance being a steel slab having a steel composition substantially consisting of iron or a slab, heated to 950 to 1150 ° C.,
Rolling is performed at 800 ° C or higher with a rolling shape ratio A of 0.6 or more at least once, and then rolling is performed at 800 ° C or lower with a reduction rate of more than 35% and 70% or less, and a plate thickness of 50 mm or more. a thick plate, good machinability, characterized in that it row de <br/> hydrogen annealing to the thick plate at 600 to 750 ° C., producing excellent good electromagnetic planks magnetic properties at medium magnetic field Method.

(Equation 3)

(2) After dehydrogenating a thick plate having a thickness of 50 mm or more, it is annealed at 750 to 950 ° C. or 910.
A method for producing a good electromagnetic thick plate having good machinability and excellent magnetic characteristics in a medium magnetic field, which is characterized in that the normalization is performed at 1000 ° C.

(3) C: 0.01% or less by weight%
Si: 0.02% or less, Mn: 0.20% or less, P:
0.02 to 0.20%, S: 0.010% or less, Al:
0.040% or less, N: 0.004% or less, O: 0.0
95% or less, H: 0.0002% or less, balance 950 to 1150
Rolling is performed by heating to 800 ° C and taking at least one rolling pass with a rolling shape ratio A of 0.6 or more at 800 ° C or more, and then 8
Rolling is performed at a temperature of 00 ° C. or lower at a rolling reduction of more than 35% and 70% or less to form a thick plate having a thickness of less than 50 mm, and the thick plate is made of 750 to 750.
A method for producing a good electromagnetic thick plate having good machinability and excellent magnetic characteristics in a medium magnetic field, characterized by being annealed at 950 ° C. or normalized at 910 to 1000 ° C.

[Equation 4]

[0008]

[Operation] First, the magnetization process will be described. When degaussed steel is put in a magnetic field and the magnetic field is strengthened, the direction of the magnetic domain gradually changes, and the magnetic domain close to the direction of the magnetic field becomes predominant and the other magnetic domains are annealed. That is, the domain wall moves. When the magnetic field is further strengthened and the movement of the domain wall is completed, the entire magnetic domain next turns to the magnetization direction.

In this magnetization process, it is the ease of movement of the domain wall that determines the magnetic flux density in a low magnetic field. That is, it can be qualitatively said that in order to obtain a high magnetic flux density in a low magnetic field, it is necessary to reduce as much as possible the obstacles to the movement of the domain wall. From this point of view, coarsening of crystal grains, which hinders the movement of the domain wall, has been an important technique in the past (Japanese Patent Laid-Open No. 60-
96749). On the other hand, there was no knowledge about a method for obtaining a high magnetic flux density in a medium magnetic field.

In order to obtain a high magnetic flux density in a medium magnetic field, the present inventors not only make the crystal grains coarse, but also
It has been found that it is important that the directions of magnetization between adjacent crystal grains are parallel to the rolling direction. Relatively coarse particles that are neither super-coarse particles nor fine particles (ferrite grain size No. 0
It was found that the magnetic properties of the medium magnetic field are significantly improved by making the (100) direction random in parallel with the rolling direction.

The hot rolling conditions for this are 800 ° C.
By taking a rolling reduction of more than 35% and 70% or less, it is possible to refine the crystal grains before heat treatment after rolling to facilitate recrystallization and to introduce strain into the steel to reduce this strain during heat treatment. By using the driving force for recrystallization, relatively large crystal grains can be stably obtained over the entire plate thickness, and at the same time,
The crystal orientation of (100) becomes random parallel to the rolling direction.

In FIG. 1, 0.005Si-0.06Mn-
The rolling reduction of 800 ° C. or less and the magnetic flux density at 5 Oe in 0.015 Al steel are shown. By reducing more than 35% and 70% or less,
A high magnetic flux density can be obtained. Further, as a means for obtaining a high magnetic flux density in a medium magnetic field, the effects of elements causing internal stress and void defects were studied in detail, and the intended purpose was achieved.

Further, as a result of various studies on the influence of void defects, it was found that those having a size of 100 μ or more significantly deteriorate the magnetic characteristics. It was found that the rolled shape ratio A needs to be 0.6 or more in order to eliminate the harmful void defects of 100 μ or more.

(Equation 5)

Furthermore, the presence of hydrogen in steel is also harmful, especially
It was found that the magnetic characteristics are significantly improved by performing dehydrogenation heat treatment on a thick plate having a thickness of 50 mm or more . High form ratio rolling reduces the size of void defects to 100μ
By reducing the hydrogen content in the steel by the following and by the dehydrogenation heat treatment, the magnetic flux density in a medium magnetic field is significantly increased.

Next, it was found that the addition of P is very effective for the machinability of this high-purity steel, especially for reducing the surface roughness after cutting. FIG. 3 shows 0.007C-0.10Mn-0.
Surface roughness of 015 Al steel at a cutting length of 10 m is 10 μm
It is defined that normal (shown by Δ), about 5 μm is good (shown by ◯), and about 1 μm is particularly good (shown by ⊚). As shown in the figure, P addition amount is 0.02%
It can be seen that in the above range, a good machinability with a surface roughness of 5 μm or less is exhibited.

Next, the reasons for limiting the components will be described. C is an element that increases the internal stress in steel and lowers the magnetic characteristics, especially the magnetic flux density in a low magnetic field, and reducing it as much as possible contributes not to decrease the magnetic flux density in a medium magnetic field. Also, from the viewpoint of magnetic aging, the lower it is, the less the deterioration with time is, and it can be used permanently with good magnetic characteristics. Therefore, the content is limited to 0.01% or less. As shown in FIG. 2, by further setting the content to 0.005% or less, a higher magnetic flux density can be obtained.

Si and Mn are preferably low in terms of magnetic flux density in a medium magnetic field, and Mn is preferably low in terms of producing MnS inclusions. From this meaning, Si is 0.02%
Hereinafter, Mn is limited to 0.20% or less. The Mn content is more preferably 0.10% or less from the viewpoint of producing MnS-based inclusions. P is an element that reduces the amount of tool wear and increases machinability, and as shown in FIG.
%, It is necessary to add more than 0.20%, but if added over 0.20%, the magnetic properties in a medium magnetic field deteriorate, so the upper limit is set to 0.
20%.

S and O form non-metallic inclusions in the steel and have a harmful effect on the coarsening of crystal grains, and the magnetic flux density decreases as the content increases, and the magnetic properties decrease, so the smaller the better. . Therefore, S is 0.010% or less and O is 0.005% or less.

Al is used as a deoxidizing agent. If the amount of Al is too large, inclusions are formed and the properties of the steel are impaired, so the upper limit is made 0.040%. Furthermore, in order to reduce AlN, which is a precipitate that hinders the coarsening of crystal grains, the lower the better, the better is 0.020%. N increases the internal stress and reduces the magnetic flux density in a medium magnetic field due to the grain refining effect of AlN, so the upper limit is made 0.004%. H
Reduces the magnetic properties and prevents the reduction of void defects, so the content is made 0.0002% or less.

Next, the manufacturing method will be described. Regarding the rolling conditions, first, the heating temperature before rolling is set to 1150 ° C. or lower. At heating temperatures higher than 1150 ° C., the variation of the heating γ grain size in the plate thickness direction is large, and this variation remains after rolling and the final Since the crystal grains become non-uniform, the upper limit is 1150.
℃. If the heating temperature is lower than 950 ° C., the deformation resistance of rolling increases, and the rolling load of rolling having a high shape ratio to eliminate void defects described below increases.
The lower limit is 50 ° C.

In hot rolling, the above-mentioned void defects are large and small in the solidification process of steel, but they always occur and means for eliminating them must be done by rolling. Therefore, the role of hot rolling is important. is there. That is, it is effective to increase the amount of deformation per hot rolling so that the deformation reaches the center of the plate thickness.

Specifically, it is necessary to carry out high shape ratio rolling including a rolling pass having a rolling shape ratio A of 0.6 or more at one temperature of 800 times or more at 800 ° C. or more to reduce the size of void defects to 100 μ or less. Good for By eliminating the void defects by the high shape ratio rolling during rolling, the dehydrogenation efficiency in the dehydrogenation heat treatment to be performed later is dramatically increased. 8 here
The reason why high shape ratio rolling is performed at a temperature of 00 ° C. or higher is that the deformation resistance is large at a low temperature of less than 800 ° C. and rolling is difficult with a normal rolling mill.

Next, at a temperature of 800 ° C. or less, the cumulative rolling reduction is made to exceed 35% to make the crystal grains finer and to introduce strain, thereby promoting recrystallization during the subsequent heat treatment. Furthermore, by this rolling, the crystal orientation of (100) is made random parallel to the rolling direction. However, if the rolling reduction exceeds 70%, the crystal grain size after heat treatment becomes non-uniform in the plate thickness direction, increasing the variation in magnetic flux density. Therefore, in order to obtain relatively coarse grains that are uniform in the plate thickness direction, the reduction rate is 35%.
More than 70%.

Next, following hot rolling, grain coarsening, removal of internal strain, and dehydrogenation heat treatment are applied to thick materials having a plate thickness of 50 mm or more. When the plate thickness is 50 mm or more, the diffusion of hydrogen is difficult, which causes void defects and, together with the action of hydrogen itself, reduces the magnetic flux density in a medium magnetic field. For this reason, dehydrogenation heat treatment is performed, but at that time, if the temperature is lower than 600 ° C., the dehydrogenation efficiency is poor, and if it exceeds 750 ° C., a part of the transformation starts, so that it is performed in the temperature range of 600 to 750 ° C. As the dehydrogenation time, various examination results [0.6 (t-50) +6]
The time (t: plate thickness) is appropriate.

Annealing is for grain coarsening and internal strain removal.
However, if the temperature is less than 750 ° C, coarsening of crystal grains occurs.
In addition, the homogeneity of the crystal grains in the plate thickness direction is higher than 950 ° C.
Since it cannot be maintained, the annealing temperature is limited to 750 to 950 ° C.
Set.

Normalization is performed by adjusting crystal grains in the plate thickness direction and removing internal strain.
The normalizing temperature is 910-1000 ° C.
limit. Below 910 ° C, austenite and fellatio
Crystal grains become mixed due to the inclusion of the iron zone, and the temperature exceeds 1000 ° C.
However, the uniformity of the crystal grains in the plate thickness direction cannot be maintained.

In order to improve the magnetic properties, the crystal grain roughness
Larger and internal distortion removal can be considered, but especially internal distortion removal
This is a mandatory condition. Internal strain removal is thicker than 50 mm
Since dehydrogenation heat treatment can be performed on the material,
For thick materials, dehydrogenation heat treatment also serves as the above-mentioned annealing or normalization.
I can sleep.

[0028]

EXAMPLES Next, examples of the present invention will be given together with comparative examples. Table 1 shows the manufacturing conditions of the electromagnetic plate thickness, the ferrite grain size, and the magnetic flux density in a medium magnetic field.

[0029]

[Table 1]

[0030]

[Table 2]

Examples 1 to 6 show examples of the present invention, and Examples 7 to
Reference numeral 23 shows a comparative example. Examples 1 to 3 are finished to a plate thickness of 100 mm, have a high magnetic flux density in a medium magnetic field, and have good machinability. Compared to Example 1, Example 2 has lower C, and Example 3 has lower Mn.
And shows higher magnetic properties. Example 4 is 40 mm, Example 5
Is 6 mm and Example 6 is 10 mm, and has a high magnetic flux density and good machinability.

In Examples 7 to 8, P is low and the machinability is not good.
Example 9 has too high P, Example 10 has high C, Example 11 has high Mn, Example 12 has high S, Example 13 has high Al, Example 14
Has a high N value, Example 15 has a high O value, and Example 16 has a high H value. In Example 17, the heating temperature exceeds the upper limit and the magnetic flux density is low.
Example 18 has a low magnetic flux density because the heating temperature deviates from the lower limit and the maximum shape ratio is small. In Example 19, the rolling reduction below 800 ° C falls below the lower limit and the magnetic flux density is low. Example 20
The maximum shape ratio is below the lower limit, Example 21 is below the dehydrogenation heat treatment temperature, and Example 22 is below the annealing temperature.
Example 23 has a low magnetic flux density because there is no dehydrogenation heat treatment.

[0033]

INDUSTRIAL APPLICABILITY The present invention has succeeded in providing a thick steel plate having a large thickness with a uniform high electromagnetic characteristic by appropriately limiting the components, and has been made applicable to a structure utilizing the magnetic characteristic of direct current magnetization. In addition, the manufacturing method thereof is a method of simultaneously performing the above-described component limitation, grain adjustment and hot dehydrogenation heat treatment after hot rolling, and provides a very economical manufacturing method, which has a great industrial effect. It is a thing.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of a rolling reduction of 800 ° C. or less on the magnetic flux density at 5 Oe.

FIG. 2 is a graph showing the influence of C content on the magnetic flux density at 5 Oe.

FIG. 3 is a graph showing the effect of P content on machinability.

Claims (3)

(57) [Claims] 1. By weight%, C: 0.01% or less, Si: 0.02% or less, Mn: 0.20% or less, P: 0.02 to 0.20%, S: 0.010% Below, Al: 0.040% or less, N: 0.004% or less, O: 0.005% or less, H: 0.0002% or less, and the balance is a steel slab or a slab with a steel composition substantially consisting of iron. 9
Rolling is performed by heating to 50 to 1150 ° C. and taking at least one rolling pass with a rolling shape ratio A of 0.6 or more at 800 ° C. or more, and subsequently, at 800 ° C. or less, a reduction ratio of more than 35% and 70% or less. Rolled into a thick plate with a thickness of 50 mm or more ,
Plank to 600-750 by dehydrogenation heat treatment line that will better machinability characterized by ° C., excellent good method for manufacturing the electromagnetic planks magnetic properties at medium magnetic field. [Equation 1] 2. After dehydrogenating a thick plate having a thickness of 50 mm or more,
Anneal at 750-950 ° C or 910-100
The method for producing a good electromagnetic thick plate having good machinability and excellent magnetic characteristics in a medium magnetic field according to claim 1, wherein normalizing is performed at 0 ° C. 3. By weight%, C: 0.01% or less, Si: 0.02% or less, Mn: 0.20% or less, P: 0.02 to 0.20%, S: 0.010% Below, Al: 0.040% or less, N: 0.004% or less, O: 0.005% or less, H: 0.0002% or less, and the balance is a steel slab or a slab with a steel composition substantially consisting of iron. 9
Rolling is performed by heating to 50 to 1150 ° C. and taking at least one rolling pass with a rolling shape ratio A of 0.6 or more at 800 ° C. or more, and subsequently, at 800 ° C. or less, a reduction ratio of more than 35% and 70% or less. Rolling is performed to form a thick plate having a thickness of less than 50 mm, and the thick plate is annealed at 750 to 950 ° C. or 910.
Good machinability characterized by normalizing at 1000 ° C,
A method for manufacturing a good electromagnetic thick plate having excellent magnetic characteristics in a medium magnetic field. [Equation 2]