JPH024918A - Manufacture of non-oriented thick electrical plate having high magnetic flux density - Google Patents

Abstract

PURPOSE:To manutacture the title thick elecrtical plate having high magnetic flux density in a low megnetic field and reduced in differences in magnetic properties in a plate-thickness direction by subjecting a steel stock with a specific composition to hot rolling under specific conditions and then to a combination ot cold rolling and annealing to form a thick steel plate. CONSTITUTION:A slab or cast slab having a composition consisting of, by welght, <=0.01% C, <=0.02% Si, <=0.20% Mn, <=0.015% P, <=0.010% S, <=0.05% Cr, <=0.01% Mo, <=0.01% Cu, 0.005-0.040% Al, <=0.004% N, <=0.005% O, <=0.002% H, and the balance essentially iron is belted to 1150-1300 deg.C and then subjected to rolling in which single or more rolling passes of >=0.7 reduction ratio A represented by an equation are applied at >=900 deg.C finishing temp. When the thickness of the resulting plate is >=50mm, this plate is subjected to dehydrogenation treatment at 600-750 deg.C, to cold rolling at 5-25% draft, and to annealing at 750-950 deg.C, and, when the thickness is 20-<50mm, this plate is subjected to cold rolling at 5-25% draft and to annealing at 750-950 deg.C. By this method, the non-oriented thick electrical plate of >=20mm thickness increased in magnetic flux density and having magnetic properties of >=0.8T magnetic flux density in a magnetic field of 80A/m can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] In recent years, with advances in elementary particle research and medical equipment, which are cutting-edge science and technology, devices that use magnetism are used in large structures, and there is a demand for improved performance. It is being

The present invention relates to a method for manufacturing a non-oriented electromagnetic thick steel plate with a high magnetic flux density for the iron core of a magnet used under DC magnetization conditions or for a magnetic shield necessary for shielding a magnetic field.

[Prior Art] It is well known that many materials including silicon steel plates and electromagnetic soft iron plates have been provided in the field of thin plates as electromagnetic steel plates with excellent magnetic flux density.

However, when used as a structural member, there are problems with assembly and strength, and it becomes necessary to use thick steel plates. Until now, electromagnetic plates have been manufactured using pure iron-based components. For example, Japanese Patent Laid-Open No. 60-96749 is known.

However, in recent years, as devices have become larger and their capabilities have improved, devices with even better magnetic properties, especially in low magnetic fields, such as 8
There is a strong demand for the development of steel materials with high magnetic flux density at 0 A/m. With the steel materials developed in the above-mentioned patents, it is not possible to stably obtain a high magnetic flux density in a low magnetic field of 80 A/m.

[Problems to be Solved by the Invention] The purpose of the present invention was to provide a non-oriented electromagnetic thick plate that has a high magnetic flux density in a low magnetic field and has small differences in magnetic properties in the thickness direction. The objective is to provide a manufacturing method.

[Means for Solving the Problems] The present invention is based on weight%, c: o, ot% or less, Si:
0.02% or less, Mn: 0.20% or less, P: 0.
015% or less, S: 0.010% or less, Cr: 0.015% or less, S: 0.010% or less, Cr: 0.
05% or less, MO: 0, old % or less, Cu: 0.01% or less, Afi: 0.005 to 0.040%, N・0.00
4% or less, O: 0.005% or less, H: 0.0002
% or less, the remainder of which is essentially iron, is heated to 1150 to 1300°C, and the finishing temperature is 90°C.
After rolling at least one rolling pass with a rolling shape ratio A of 0.7 or more under conditions of 0°C or higher, the plate thickness is 50 mm.
For the above-mentioned thick plates, after dehydrogenation heat treatment at 600-750℃, cold rolling at a reduction rate of 5-25%, and then annealing at 750-950℃, the plate thickness is 20mm or more.
A plate having magnetic properties with a magnetic flux density of 0.8 Tesla or more in a magnetic field of 80 A/m, characterized by cold rolling with a rolling reduction of 5 to 25% for thicknesses of less than 0 mm, and then annealing at 750 to 950°C. This is a method for manufacturing a non-directional electromagnetic thick plate having a thickness of 20+am or more and having a high magnetic flux density.

However, A = (2117 shoulder 1 stone "ro")/h, 10hI Q
10 A: Relative to rolled shape,: Inlet side plate thickness (related) h: Outlet side plate thickness (mm) R: Roll radius (stop) [Function] First, magnetization is applied to increase the magnetic flux density in a low magnetic field. Describing the process, when demagnetized steel is placed in a magnetic field and the magnetic field is strengthened, the orientation of the magnetic domains gradually changes.
The magnetic domains close to the direction of the magnetic field become dominant and merge with other magnetic domains. In other words, movement of the domain wall occurs.

When the magnetic field becomes stronger and the movement of the domain wall is completed, the direction of the magnetic force of the entire magnetic domain changes direction. In this magnetization process, the ease with which domain walls move determines the magnetic flux density in low magnetic fields.

In other words, it can be said qualitatively that in order to obtain a high magnetic flux density in a low magnetic field, it is necessary to reduce as much as possible what impedes the movement of domain walls.

Here, as a means to obtain high magnetic flux density in a low magnetic field, the inventors conducted a detailed study on the effects of grain size, elements that cause internal stress, and void defects, and first, in order to coarsen the grains, In the present invention, we have found appropriate conditions in which abnormal grain growth occurs and the ferrite grain size grows coarsely by introducing working strain by cold rolling and subsequent annealing, which was not possible in the past in thick plate rolling.

Figure 1 shows the influence of cold rolling rate on ferrite grain size.

At cold rolling ratios of 5 to 25%, centering around 10%, a significant coarsening of the crystal ratio occurs. In addition, Ag is used to reduce A47N, which has a crystal grain refining effect.

In order to reduce the amount of N and the manufacturing method, it is necessary to raise the heating temperature as much as possible to coarsen the heated austenite grains, and to make the rolling finishing temperature as high as possible.

As an elemental influence for reducing internal stress, a reduction in C is necessary. 0.01SiO,L Mn shown in Figure 2
In -0,01AN steel, the magnetic flux density in a low magnetic field (80 A/m) decreases as the C content increases.

Furthermore, as a result of various studies on the influence of gap defects, it was found that the size of gap defects of 100 μm or more significantly deteriorates the magnetic properties. It has also been found that in order to eliminate harmful void defects of 100 microns or more, the rolled shape ratio A needs to be 0.7 or more.

Furthermore, the presence of hydrogen in steel is also harmful, as shown in Figure 3, and it has been found that dehydrogenation heat treatment can significantly improve magnetic properties. 0.007 as shown in Figure 3
- C-0, OIS i -0, I In Mn steel, the size of porosity defects is reduced to 100μ or less by high shape ratio rolling, and the hydrogen in the steel is reduced by dehydrogenation heat treatment, thereby increasing the magnetic flux in a low magnetic field. It can be seen that the density increases significantly.

Furthermore, it is also important to ensure homogeneity of magnetic properties, and it has been confirmed that the method according to the present invention is an extremely effective means for this as well.

Next, the reason for limiting the ingredients of the present invention will be described.

C is an element that increases the internal stress in steel and lowers the magnetic properties, particularly the magnetic flux density in a low magnetic field, the most, and reducing it as much as possible contributes to not reducing the magnetic flux density in a low magnetic field. In addition, from the viewpoint of magnetic aging, the lower the content, the less deterioration over time and the ability to use it permanently with good magnetic properties.For this reason, the content is limited to 0.010% or less.

As shown in FIG. 1, an even higher magnetic flux density can be obtained by reducing the amount to 0.005% or less.

The lower the Si and Mn content, the better from the viewpoint of magnetic flux density in a low magnetic field, and the lower the Mn content, also from the viewpoint of generating MnS-based inclusions. From this meaning, Sl is 0.02% or less and Mn is 0.
．． Limited to 20% or less. Regarding Mn, from the point of view of forming MnS-based inclusions, it is more desirable that it be 0.10% or less.

P, s, and o form nonmetallic inclusions in steel and segregate, thereby hindering the movement of domain walls, and as their content increases, the magnetic flux density decreases, resulting in a decrease in magnetic properties. So the less the better. Therefore, P is 0
．． 015% or less, S is 0.010% or less, O is 0.00
It was set to 596 or less.

Cr, Mo, and Cu reduce the magnetic flux density in a low magnetic field, so the smaller the better, and in order to reduce the degree of segregation, it is necessary to keep them as low as possible.
r is 0.05% or less, Mo is 0.01% or less, Cu is 0
,01% or less.

Al is used as a deoxidizing agent and is an essential element for homogenizing the internal quality when the plate is thick as in the present invention.
The upper limit is set to 0.040% or less, since too much may generate inclusions and impair the properties of the steel. Furthermore, in order to reduce AlN, which has a crystal grain refining effect, the content is desirably 0.020% or less.

The upper limit is 0 because N increases the internal stress and AρN reduces the magnetic flux density in a low magnetic field due to the grain refinement effect.
．． 0.004% or less.

Since H deteriorates electromagnetic properties and prevents the reduction of void defects, it is set to 0.0002% or less.

Next, the manufacturing method will be described.

Regarding the rolling conditions, first, the heating temperature before rolling was set to 1150°C.
The reason for this is to coarsen the heated austenite grains and improve the magnetic properties. Since heating above 1300°C is unnecessary from the viewpoint of preventing scale loss and saving energy, the upper limit was set at 1300°C.

As for the rolling finishing temperature, if the finishing temperature is below 900℃, the crystal grains will become finer due to low-temperature rolling, and the magnetic properties will deteriorate.
℃ or higher.

Furthermore, in hot rolling, the role of hot rolling is important because the above-mentioned porous defects are inevitably generated during the solidification process of steel, and rolling is the only way to eliminate them. be.

That is, hot rolling in which the amount of deformation per hot rolling is increased and the deformation extends to the center of the plate thickness is effective. Specifically, high shape ratio rolling including one or more rolling passes with rolling shape ratio A of 067 or more is performed, and the size of the void defects is reduced to 100.
Setting it below μ is good for electromagnetic properties.

By eliminating void defects during rolling by this high shape ratio rolling, the dehydrogenation efficiency in the subsequent dehydrogenation heat treatment is dramatically increased.

Next, following hot rolling, thick materials with a thickness of 50 mm or more are subjected to dehydrogenation heat treatment. If the plate thickness is 50 mm or more, it is difficult for hydrogen to diffuse, which causes void defects.
In addition, combined with the action of hydrogen itself, it lowers the magnetic flux density in a low magnetic field.

For this reason, dehydrogenation heat treatment is performed, but if the dehydrogenation heat treatment temperature is less than 600°C, the dehydrogenation efficiency is poor;
If the temperature exceeds .degree. C., transformation will partially start, so the temperature range is 600 to 750.degree.

As a result of various studies, the dehydrogenation time [0.8 (t50)
+6) Time (t: plate thickness) is appropriate.

Furthermore, by combining cold rolling and annealing, we aim to coarsen the ferrite grain size through abnormal grain growth. The cold rolling rate is preferably 5 to 25% as shown in FIG. Annealing is carried out to coarsen the crystal grains and remove internal strain. At temperatures below 750°C, coarsening of the crystal grains does not occur, and at temperatures above 950°C, the homogeneity of the crystal grains in the thickness direction cannot be maintained. The temperature is limited to 750 to 950°C.

On the other hand, when the plate thickness is 20 mrn or more and less than 50 mm, hydrogen can easily diffuse, so dehydrogenation heat treatment is not necessary and only the cold rolling and annealing described above are required.

[Example] Table 1 shows the manufacturing conditions of the electromagnetic plate, the ferrite grain size, and the magnetic flux density in a low magnetic field.

] 2 Examples 1 to 10 show examples of the present invention, and Examples 11 to 31 show comparative examples.

Examples 1 to 5 were finished to a plate thickness of about 120 mm and exhibit uniform, coarse grains and high magnetic properties. Compared to Example 1, Example 2 has a low C, Examples 3 and 4 have a low Mns, and Example 5 has a low Aρ, showing higher magnetic properties. Examples 6-8 are 550mm, Example 9 is 50m
m, Example 10 is finished to 20 mm, has uniform and coarse grains, and exhibits high magnetic properties.

Example ■1 has high C, Example 12 has high SL, Example 13 has high M mouth, Example 14 has high P, Example 15 has high S, and Example 16
is high in Cr, Example 17 is high in MO, Example 18 is high in Cu, Example 19 is high in A and Ill, Example 20 is high in N, Example 21 is high in 0, Example 22 is high in H, respectively. Since it exceeds the upper limit, the magnetic property value is low.

In Example 23, the heating temperature was outside the lower limit, in Example 24, the rolling finish temperature was outside the lower limit, in Example 25, the maximum shape ratio was outside the lower limit, in Example 26, the dehydrogenation heat treatment humidity was outside the lower limit, and in Example 27.
The annealing temperature exceeds the lower limit in Example 28, the annealing temperature exceeds the upper limit in Example 29, there is no dehydrogenation heat treatment in Example 30, there is no cold rolling in Example 30, and the cold rolling rate exceeds the upper limit in Example 31, resulting in low magnetism. It is a characteristic value.

[Effects of the Invention] As described in detail above, according to the present invention, by appropriately limiting the ingredients and by combining cold rolling and annealing, which was unthinkable in conventional thick plate rolling, thick steel plates can be uniformly rolled. We succeeded in providing high electromagnetic properties, making it applicable to structures that utilize magnetic properties due to direct current magnetization.
This has great industrial effects.

[Brief explanation of the drawing]

Figure 1 is a graph showing the effect of cold rolling rate on ferrite grain size, Figure 2 is a graph showing the effect of C content on magnetic flux density at 80A/m, and Figure 3 is a graph showing the effect of C content on magnetic flux density at 80A/rn.
3 is a graph showing the influence of the size of void defects and dehydrogenation heat treatment on the magnetic flux density in FIG. Agent Patent Attorney Tatsuo Chanoki Diagram 'A? −Threshold rolling cell (%) Fig.? θ Diagram 3)

Claims (1)

[Claims] In weight %, C: 0.01% or less, Si: 0.02% or less, Mn: 0.20% or less, P: 0.015% or less, S: 0.010% or less, Cr: 0.05% or less, Mo: 0.01% or less, Cu: 0.01% or less, Al: 0.005 to 0.040%, N: 0.004% or less, O: 0.005% or less , H: 0.0002% or less, and the remainder is substantially iron.
A thick plate with a thickness of 50 mm or more is heated to 50 to 1300°C and rolled with at least one rolling pass with a rolling shape ratio A of 0.7 or more under conditions where the finishing temperature is 900°C or higher. After dehydrogenation heat treatment at 600 to 750°C, cold rolling was performed at a reduction rate of 5 to 25%, and then 750°C
Magnetic field 8 characterized by performing annealing at ~950°C, cold rolling at a reduction rate of 5 to 25% for plate thicknesses of 20 mm or more and less than 50 mm, and then annealing at 750 to 950°C.
A method for manufacturing a non-directional electromagnetic thick plate having a thickness of 20 mm or more and having a high magnetic flux density and having magnetic properties with a magnetic flux density of 0.8 Tesla or more at 0 A/m. However, A=(2√R(h_i-h_o))/h_i+h_o A: Rolling shape ratio h_i: Inlet side plate thickness (mm) h_o: Outlet side plate thickness (mm) R: Roll radius (mm)