JPH0711328A - Manufacturing method of good electromagnetic thick plate - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a method for manufacturing a good electromagnetic thick plate. [Structure] C: 0.01% or less, Si: 0.10-3.
5%, S: 0.02% to 0.20%, Al:
950 ~ 1150 ℃ heating with 0.040% or less of the component system,
Rolling with a rolling shape ratio of 0.6 or more at 800 ° C or more and a rolling reduction of 3
A method for producing a good electromagnetic thick plate having good machinability and excellent magnetic properties in a medium magnetic field by rolling 5 to 70% and performing dehydrogenation heat treatment, annealing or normalization depending on the plate thickness. [Effect] Good machinability and excellent magnetic characteristics in medium magnetic field.

Description

Detailed Description of the Invention

[0001]

[Industrial field of application] With recent advances in elementary particle research and medical equipment, which are the most advanced science and technology, devices that use magnetism for large structures are used, and their performance is required to be improved. In addition to high saturation magnetic flux density, 5Oe (400A / 400A /
Although a high magnetic flux density in a medium magnetic field near (m) is required,
Furthermore, good machinability during processing is also required. That is, 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 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. However, there are problems in assembling and strength when used as a structural member, 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 size of equipment and improvement in capacity, magnetic properties are even better, especially in medium magnetic fields such as 5 Oe.
There is a strong demand for development of steel materials with high magnetic flux density near (400 A / m). With the steel materials developed by the above patents, etc., a high magnetic flux density of a medium magnetic field in the vicinity of 5 Oe is not stably obtained.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a good electromagnetic thick plate which has good machinability and excellent magnetic characteristics in a medium magnetic field. is there.

[0004]

The present invention is based on weight percent C
: 0.01% or less, Si: 0.10% or less,
3.5% or less, Mn: 0.20% or less, S:
0.02% or more, 0.20% or less, Al: 0.040%
Below, N: 0.004% or less, O: 0.005
% Or less, H: 0.0002% or less, the balance is 950 to 115
Rolling is carried out by heating to 0 ° C. and taking at least one rolling pass at which the rolling shape ratio A becomes 0.6 or more according to the following formula (1) at 800 ° C. or more, and subsequently, at 800 ° C. or less, the reduction ratio is 35.
For 70% or more thick plates, if necessary, after dehydrogenation heat treatment at 600 to 750 ° C., annealing at 750 to 950 ° C. or at 910 to 1000 ° C. Normalize and, if the plate thickness is less than 50 mm, anneal at 750 to 950 ° C or 910-1
This is a method for producing a good electromagnetic thick plate having good machinability and excellent magnetic properties in a medium magnetic field, which is characterized by normalizing at 000 ° C.

[0005]

[Equation 2]

[0006]

[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. It is the ease of movement of the domain wall that determines the magnetic flux density in the low magnetic field in this magnetization process. 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 viewpoint, it has been an important technique to coarsen the crystal grains in order to reduce the crystal grain boundaries which obstruct the movement of the domain wall (see Japanese Patent Laid-Open No. 96749/1985). 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 was found that it is important that the directions of magnetization between adjacent crystal grains are aligned parallel to the rolling direction. Relatively coarse particles that are neither super-coarse particles nor fine particles (ferrite grain size No. 0
It has been found that the magnetic characteristics of the medium magnetic field are significantly improved by making the [100] direction random in parallel to the rolling direction. As a hot rolling condition for this purpose, a rolling reduction of not less than 35% and not more than 70% at 800 ° C. or less facilitates refining and recrystallization of crystal grains before heat treatment after rolling and strain in steel. By introducing this strain as a driving force for recrystallization during heat treatment, relatively large crystal grains can be stably obtained over the entire plate thickness, and at the same time, the [100] crystal orientation becomes parallel to the rolling direction. It will be random.

In FIG. 1, 1.7Si-0.06Mn-0.0
The reduction rate of 800 ° C. or less and the magnetic flux density at 5 Oe in 15 Al steel are shown. A high magnetic flux density is obtained by the reduction of 35 to 70%. 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.
In addition, as a result of various studies on the effect of void defects,
It has been found that a magnetic powder having a size of 100 μ or more significantly deteriorates magnetic characteristics. And this 100μ
It was found that the rolling shape ratio A calculated by the following formula (1) is required to be 0.6 or more in order to eliminate the above-mentioned harmful void defects.

[0009]

[Equation 3]

Further, it was found that the presence of hydrogen in steel is also harmful, and the magnetic properties are significantly improved by performing the dehydrogenation heat treatment. The high-shape-ratio rolling reduces the size of void defects to 100 μm or less, and the dehydrogenation heat treatment reduces hydrogen in the steel, thereby significantly increasing the magnetic flux density in a medium magnetic field.

With regard to the constituent elements, it has been found that particularly in the present manufacturing method, addition of Si is very effective for obtaining a high magnetic flux density in a low magnetic field. Figure 2 is 0.008C
Fig. 3 shows the influence of Si content on the magnetic flux density in a medium magnetic field (5 Oe) in a -0.10 Mn steel. In this manufacturing method, the Si content is 0.1 to 3.5%, particularly 0.6 to
A high magnetic flux density is shown in the range of 2.5%.

Next, it was found that the addition of S is very effective for the machinability of the high purity steel, especially for reducing the surface roughness after cutting. FIG. 3 shows 0.8Si-0.11Mn-0.0.
For 14 Al steel, the surface roughness at a cutting length of 10 m is normal (indicated by Δ), approximately 5 μm is good (indicated by ◯), and approximately 1 μm is particularly good (indicated by ⊚). ing. As shown in the figure, S 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.

The reasons for limiting the components will be described below. 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. 4, by further setting the content to 0.005% or less, a higher magnetic flux density can be obtained. Si is an element that is more advantageous to add in terms of magnetic flux density in a medium magnetic field. As shown in FIG.
To 3.5%, and more preferably 0.6 to 2.
Add in the range of 5%.

The Mn content is preferably low in terms of magnetic flux density in a medium magnetic field, and the Mn content is preferably low in terms of forming MnS-based inclusions. From this meaning, Mn is limited to 0.20% or less. The content of Mn is more preferably 0.10% or less from the viewpoint of forming MnS-based inclusions. S is an element that reduces the amount of tool wear and increases machinability, and it is necessary to add 0.02% or more as shown in FIG.
If added over 20%, the magnetic properties in a low magnetic field are deteriorated, so the upper limit is made 0.20%.

O forms non-metallic inclusions in steel,
The smaller the content, the better because the magnetic flux density decreases as the content increases, which causes a hindrance to the coarsening of crystal grains. Therefore, O is set to 0.005% or less. Al is used as a deoxidizing agent, and if too much Al forms inclusions and impairs the properties of steel, the upper limit is 0.040%. Furthermore, in order to reduce AlN, which is a precipitate that hinders crystal grain coarsening, the lower the better, the better, and preferably 0.020% or less. 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 the hot rolling, the above-mentioned void defects are large and small in the solidification process of steel, but they are always generated and the 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, high shape ratio rolling including one or more rolling passes with a rolling shape ratio A of 0.6 or more is performed,
It is good for the magnetic properties that the size of the void defects is 100 μm or less. 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.

Next, at a temperature of 800 ° C. or lower, the cumulative rolling reduction is set to 35% or more to make the crystal grains finer and to introduce strain, thereby promoting recrystallization during the subsequent heat treatment. Further, by this rolling, the [100] crystal orientation 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, and variations in magnetic flux density increase. Therefore,
In order to obtain relatively coarse grains that are uniform in the plate thickness direction, the rolling reduction is 35 to 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 as needed. When the plate thickness is 50 mm or more, hydrogen is difficult to diffuse, which causes void defects and also reduces the magnetic flux density in a low magnetic field in combination with the action of hydrogen itself. 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] hours (t: plate thickness) are suitable.

Annealing is carried out for the purpose of coarsening the crystal grains and removing internal strain, but if the temperature is lower than 750 ° C., the coarsening of the crystal grains does not occur, and if it is higher than 950 ° C., the homogeneity of the crystal grains in the plate thickness direction cannot be maintained. Therefore, the annealing temperature is limited to 750 to 950 ° C. Normalization is performed to adjust crystal grains in the plate thickness direction and remove internal strain, but the lower limit is Ac, which is the lower limit of the austenite range.
_Since the homogeneity of the crystal grains in the plate thickness direction cannot be maintained at _three points of 910 ° C or higher and 1000 ° C or higher, the normalizing temperature is limited to 910 to 1000 ° C. This annealing or normalization can be performed by the dehydrogenation heat treatment performed on a thick material having a plate thickness of 50 mm or more. On the other hand, if the plate thickness is less than 50 mm, hydrogen can be easily diffused, and thus dehydrogenation heat treatment is not necessary and only the above-mentioned annealing or normalization is required.

[0021]

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

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

Examples 1-6 show examples of the present invention, examples 7-
24 shows a comparative example. Examples 1 to 3 are finished to a plate thickness of 150 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 50 mm, Example 5
Is 6 mm and Example 6 is 20 mm, and has a high magnetic flux density and good machinability. In Examples 7 and 8, S is low and the machinability is not good. Example 9 has too high S, Example 10 has high C, Example 11
Has low Si, Example 12 has high Si, Example 13 has high Mn, Example 14 has high Al, Example 15 has high N, Example 16 has high O, Example 17 has high H, and each has low magnetic properties. It is a characteristic value. In Example 18, the heating temperature exceeds the upper limit and the magnetic flux density is low. In Example 19, the heating temperature deviates from the lower limit and the magnetic flux density is low. In Example 20, the rolling reduction below 800 ° C. is below the lower limit and the magnetic flux density is low. In Example 21, the maximum shape ratio deviates from the lower limit, in Example 22, the dehydrogenation heat treatment temperature deviates from the lower limit, in Example 23, the annealing temperature deviates from the lower limit, and in Example 24, the dehydrogenation heat treatment does not occur, so that the magnetic flux density is low.

[0027]

As described in detail above, according to the present invention, it has been possible to provide a thick steel plate having a large thickness with a uniform high electromagnetic characteristic by appropriately limiting the components, and to utilize the magnetic characteristic of direct current magnetization. It is applicable to structures,
In addition, the manufacturing method is also a method in which the above-described component limitation, grain adjustment after hot rolling, and dehydrogenation heat treatment are simultaneously performed, and it provides a very economical manufacturing method, which has a great industrial effect.

[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 effect of Si content on the magnetic flux density at 5 Oe.

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

FIG. 4 is a graph showing the influence of C content on the magnetic flux density at 5 Oe.

Claims (1)

[Claims] 1. By weight%, C: 0.01% or less, Si: 0.10% or less, 3.5% or less, Mn: 0.20% or less, S: 0.02% or more, 0.20. % Or less, 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 having a steel composition substantially composed of iron or casting. 9 pieces
Heating at 50 to 1150 ° C., one rolling pass at which the rolling shape ratio A becomes 0.6 or more according to the following equation (1) at 800 ° C. or more
Rolling is performed more than once, and then rolling is performed at a temperature of 800 ° C. or lower at a reduction rate of 35 to 70%. For thick plates with a thickness of 50 mm or more, dehydrogenation heat treatment at 600 to 750 ° C. is performed as necessary. After that, annealing at 750-950 ℃ or normalizing at 910-1000 ℃, plate thickness 50mm
For less than, a method for producing a good electromagnetic thick plate having good machinability and excellent magnetic characteristics in a medium magnetic field, characterized by annealing at 750 to 950 ° C or normalizing at 910 to 1000 ° C. [Equation 1]