JPH06145797A - Manufacturing method of electromagnetic thick plate for magnetic shield structure - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a method for manufacturing an electromagnetic plank for a magnetic shield structure. [Constitution] Si contains 0.2% or more and less than 1.5%, Al contains 0.1% or more and less than 1.5%, or both, and Si + Al is less than 1.5% by weight.
Containing 1.0% or less of Mn and 0.02% of P according to strength
0.1% or less, B 0.003% or more, 0.
It is a component system containing 005% or less and limiting the upper limits of C, S, N, O and H, and is heated to 950 to 1100 ° C., and 800 ° C.
Rolling with a rolling shape ratio of 0.6 or more and 700 to 900 ° C.
Rolling at a rolling reduction of 35 to 70% at 900 to 105
Heat treatment at 0 ° C. [Effect] It is possible to obtain a structural electromagnetic thick plate which is excellent in strong magnetic field magnetic shielding property, strength, low temperature toughness, machinability, and cutting surface accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a method for manufacturing an electromagnetic thick plate for a magnetic shield structure.

[0002]

2. Description of the Related Art In recent years, researches on elementary particles using a strong magnetic field by superconductivity and technological developments such as power generation and power storage have been actively conducted. A magnetic shield is indispensable for shielding a strong magnetic field in these devices, and iron-based materials are widely used as relatively inexpensive magnetic shield materials. In order to effectively shield a strong magnetic field such as a superconducting device, magnetic properties are excellent in a wide range from a high magnetic field to a relatively low magnetic field, that is, a high saturation magnetic flux density and a magnetizing force of 10 Oe (80 A /
m) It is required to have a high magnetic flux density in a low magnetic field region. In addition, as the size of the equipment increases, a large amount of steel material is required for the magnetic shield, so it is advantageous to design the building itself with steel material that has a magnetic shield effect, and a material that has both strength and toughness as a structural member has recently become particularly popular. There is an increasing need. Of these, superconducting devices are often used at low temperatures, so low temperature toughness is important. Further, easiness of cutting, that is, machinability and accuracy of finished surface of cutting are important requirements. When steel is used as a structure, the welded parts are often assembled with bolts etc. because their magnetic properties are greatly reduced.
Even if there is a slight gap in the seam, leakage of the magnetic field will occur and the magnetic shield effect will be greatly reduced, so the precision of the finished surface becomes more important. That is, there is a demand for a material having all of magnetic shielding characteristics against a strong magnetic field, strength, low temperature toughness, excellent machinability, and cutting surface finish accuracy.

Up to now, Japanese Patent Laid-Open Nos. 60-208418 and 3-271325 have been known as high-strength electromagnetic thick plates, but the machinability is not considered at all.
On the other hand, JP-A-1-10831 discloses an electromagnetic thick plate having excellent machinability.
Although there is Japanese Patent Publication No. 5, the strength is low because it is a component close to pure iron. Furthermore, the inventors of the present invention have found that they have excellent machinability, as disclosed in Japanese Patent Application Nos. 3-57044 and 3-57045.
There is an invention proposed in Japanese Patent Application No. 3-57046, and in particular, the invention of Japanese Patent Application No. 3-57046 is excellent in strong magnetic field magnetic shielding property. This is characterized by adding a large amount of P to improve the machinability.
If the P content is high, there is a problem that the precision of the machined surface decreases, and the toughness at low temperatures also decreases. Japanese Patent Application No. 3-57046 does not take into consideration the precision of cutting surface finish and the low temperature toughness, and is not suitable for a new use as a structural material.
Therefore, a material having all of magnetic shield characteristics against a strong magnetic field, strength, low temperature toughness, machinability, and cutting surface finish accuracy has not been obtained so far.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has magnetic properties excellent in strong magnetic field magnetic shielding property, that is, high saturation magnetic flux density and magnetizing force of 10 Oe (80 A /
Electromagnetic thickness for magnetic shield structure that has a high magnetic flux density in a low magnetic field region of about m) and that satisfies all of the high strength according to the application, high toughness at low temperature, machinability and cutting surface accuracy. It is intended to provide a method for manufacturing a plate.

[0005]

In order to achieve the above object, the present invention provides (1)% by weight, C: 0.008% or less, Si: 0.20% or more, less than 1.5%, and Al:
One or both of 0.10% or more and less than 1.5%, and Si + Al less than 1.5%, Mn:
More than 0.2%, 1.0% or less, P: more than 0.02%, 0.10% or less, S: 0.005% or less, N:
0.004% or less, O 2: 0.006% or less, H 2:
0.0002% or less, B: 0.0003% or more, 0.
A steel slab or slab having a steel composition of 005% or less and the balance iron and unavoidable impurities is heated to 950 to 1100 ° C.,
Rolling is performed at least once in a rolling pass at a rolling shape ratio A of 0.6 or more specified by the following formula at 00 ° C or more, and then a cumulative rolling reduction is over 35% in a temperature range of 700 ° C or more and 900 ° C or less. After rolling to 70% or less, plate thickness 50 mm
The above thick plates are subjected to a dehydrogenation treatment at 600 to 750 ° C. and then annealed or standardized at 900 to 1050 ° C. For the plate thicknesses less than 50 mm, 900 to 1050 ° C.
A method for manufacturing an electromagnetic thick plate for a magnetic shield structure, which comprises annealing or normalizing at ℃.

[Equation 5]

(2) In wt%, C: 0.008% or less, Si: 0.20% or more, less than 1.5% and Al:
One or both of 0.10% or more and less than 1.5%, and Si + Al less than 1.5%, Mn:
0.2% or less, P: more than 0.02%, 0.10% or less, S: 0.01% or less, N: 0.004% or less,
O: 0.006% or less, H: 0.0002% or less,
B: 0.0003% or more and 0.005% or less, a steel slab or a slab having a steel composition consisting of the balance iron and unavoidable impurities is heated to 950 to 1100 ° C, and a rolling shape ratio defined by the following formula at 800 ° C or more. Rolling is performed with one or more rolling passes for A of 0.6 or more, and then 700 ° C or more and 900 or more.
With respect to a thick plate having a plate thickness of 50 mm or more, which is subjected to rolling with a cumulative rolling reduction of more than 35% and 70% or less in a temperature range of ℃ or less, after performing dehydrogenation heat treatment at 600 to 750 ° C,
Annealing or normalizing at 900 to 1050 ℃, plate thickness 50mm
The method for manufacturing an electromagnetic thick plate for a magnetic shield structure is characterized by annealing or normalizing at less than 900 to 1050 ° C.

[Equation 6]

[0007]

As described above, Japanese Patent Application No. 3-5 proposed by the present inventors as a steel having machinability and magnetic shielding properties.
There is a steel shown in No. 7046 to which P is added together with Si or Al, but problems when using it as structural steel are low temperature toughness, cutting surface finish accuracy and strength. As a result of studying more components and manufacturing conditions, the present inventors have decided to use B as a means for obtaining high toughness at low temperature and cutting surface accuracy while maintaining the excellent magnetic properties and machinability. It was found that the addition is extremely effective.

The reason why P deteriorates the low temperature toughness and the accuracy of the finished surface for cutting is that the grain boundaries are significantly weakened. Since the electromagnetic thick plate has an extremely low C, if the amount of P is large, grain boundary fracture is extremely likely to occur and the low temperature toughness is greatly reduced. Regarding the accuracy of the finished surface, P reduces the cutting resistance, so it works in the direction of improvement up to a certain amount of addition. However, if a large amount is added to cause grain boundary fracture, the grain size becomes very coarse due to the heat treatment, and the unit of fracture due to grain boundary fracture is large, which causes unevenness on the finished surface. Therefore, the accuracy of the finished surface is reduced. On the other hand, the effect of B is mainly that the solid solution B strengthens the grain boundary to suppress grain boundary fracture contrary to P, thereby improving the low temperature toughness and cutting surface finish accuracy. Further, solid solution B hardens the material and improves the machinability, so P
It is possible to suppress the amount of addition, and this aspect also has an advantageous effect on improving the low temperature toughness and the accuracy of the cut surface.

FIG. 1 shows 0.003% C-0.7% Si-
B and P using 0.4% Mn-0.2% Al as a base component
Various slabs with different composition of 1050 ℃
After heating to 900 ° C., a rolling pass with a rolling shape ratio A of 0.7 was taken once at 900 ° C., and subsequently, a steel plate with a thickness of 20 mm was obtained by rolling with a cumulative reduction of 60% in the range of 700 to 900 ° C. It is the result of measuring the surface roughness as an index of accuracy. The average surface roughness Rz of 10 points is 10 μm.
The following are extremely good (⊚), 20 μm or less are good (∘),
Those having a thickness of more than 20 μm were evaluated as defective (Δ). P
The amount tends to improve up to 0.06%, but if the amount exceeds 0.06%, it worsens, and after all, the addition of P alone does not provide a good cutting surface finish accuracy. On the other hand, the addition of B greatly improves the accuracy of the cutting surface, and the P amount is 0.02% or more, and the P.
If it is 12% or less, good cutting surface accuracy is obtained.

FIG. 2 shows the effects of B and P on the flank wear width during drilling as an evaluation index of machinability in the same various steels as in FIG.
That is, it is the relationship between the wear width of the drill flank and the amount of B when 40 holes with a depth of 30 mm are opened under the conditions of a rotational speed of 700 rpm and a feed rate of 150 mm / min with a high-speed steel drill,
The machinability is particularly good when the wear width is 0.2 mm or less (shown by ⊚), the machinability is good by 0.2 to 0.3 mm (shown by ◯), and the machinability is normal when 0.3 mm or more. (Indicated by △)
Is defined as The machinability is improved by adding B, and the amount of more than 0.04% is required when P is added alone.
If B is added, it may be added in an amount exceeding 0.02%. That is, B is added, and P is 0.02% or more and 0.12%.
Addition below makes it possible to obtain steel having excellent machinability and cutting surface accuracy.

The low temperature toughness is required to have a Charpy toughness of about 40 J or more at -40 ° C. in consideration of outdoor use in cold regions. Figure 3 shows low temperature (-40
C.) The effect of B and P on toughness. When P exceeds 0.04%, the low temperature toughness is poor, but the addition of B improves the toughness and P
It has a toughness value of 40 J or more even at about 0.1%.

B has the effect of improving the magnetic characteristics.
B forms a BN, traps N, and prevents the formation of AlN, which hinders the coarsening of crystal grains, thereby having a coarsening effect, which contributes to the improvement of magnetic characteristics. Furthermore B
Also increases the strength of the material as a hardening element.

The inventors have made various studies on the manufacturing process conditions, and in order to meet these various purposes,
We have found that heat treatment conditions are very important. That is,
In order to exert advantageous effects on all of strength, machinability, cutting surface accuracy, low temperature toughness, and magnetic properties, it is necessary that a suitable amount of solid solution B be present, and for that purpose heat treatment conditions are limited to a certain range. Is essential. That is, the rolling heating temperature is 9
It is necessary to set the temperature to 50 to 1100 ° C and the heat treatment temperature after rolling to 900 to 1050 ° C. Regarding the rolling conditions, first, the heating temperature before rolling is set to 1100 ° C. or less because when AlN is completely solid-dissolved, BN is excessively formed and the effect of solid solution B is hindered. However, 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 for eliminating void defects described below increases, so 950 ° C is set as the lower limit. Regarding the heat treatment temperature after rolling, it is necessary to perform heat treatment at 900 ° C. or higher in order to sufficiently coarsen the grains. But 1
If the temperature is 050 ° C. or higher, the effect of B will be significantly reduced, so it is necessary to limit the annealing or normalizing temperature to 900 to 1050 ° C.

The amount of N is also important for the effective use of B.
If the content is large, the amount of solid solution B decreases, so 0.004% or less is essential. As described above, B properly acts on any of strength, low temperature toughness, machinability, cutting surface finish accuracy, and magnetic properties, if heat treatment conditions and the like are properly selected, and B is used as a magnetic shield electromagnetic material as a structural material. It is the most important element in the present invention for the purpose of providing a thick plate.

There are some additional manufacturing requirements to obtain good magnetic properties. First, in order to obtain a high magnetic flux density in a relatively low magnetic field of about 1 Oe, it is important that the crystal grains are coarsened and the easy-magnetization [100] orientations of the crystal grains are aligned parallel to the rolling surface. Is. In the composition steel of the present invention, if a cumulative rolling reduction of more than 35% and 70% or less is taken as a hot rolling condition in the temperature range of 700 ° C. to 900 ° C., the grain size number of ferrite is 0 in addition to the effect of coarsening B. It is possible to stably obtain a large crystal grain of about −2 through the entire thickness of the plate, and at the same time, to obtain a texture in which the [100] crystal orientation is parallel to the rolling direction.

In order to obtain a high magnetic flux density in a lower magnetic field, it is also important to eliminate void defects of 100 μ or more. For that purpose, the rolling shape ratio obtained by the following formula in the temperature range of 800 ° C. or more is used. It is necessary that A be 0.6 or more.

[Equation 7]

Further, the presence of hydrogen in the steel is also harmful, and the dehydrogenation heat treatment significantly improves the magnetic properties. High form ratio rolling reduces the size of void defects to 100μ
By reducing the hydrogen content in the steel by dehydrogenation heat treatment depending on the plate thickness below, the magnetic flux density in a low magnetic field is significantly increased.

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 properties, especially the magnetic flux density in a low magnetic field, and reducing it as much as possible contributes to not lowering the magnetic flux density in a low magnetic field. Further, the lower the better, the better the toughness. From this, 0.01%
Limited to:

Si and Al are elements that are more advantageous to add from the viewpoint of magnetic flux density in a low magnetic field. Since Si has a high magnetic flux density in a low magnetic field in the range of 0.2% or more and Al in the range of 0.1% or more, either or both of Si and Al are added in this range. However, if both Si and Al are added excessively, it causes toughness deterioration and also causes a decrease in saturation magnetic flux density.
Moreover, the sum of the weight percentages of Si and Al is limited to less than 1.5%. From the viewpoint of magnetic properties, it is desirable to add Si by 0.6% or more and Al by 0.3% or more.

Mn is effective as an element for increasing the strength, and is added according to the required strength. However, when the Mn amount is large, MnS is formed, and the crystal grains are made fine to reduce the magnetic flux density. Therefore, when the Mn amount is added in excess of 0.2%, S is reduced to 0.005% or less. It is necessary to suppress the formation of MnS. If Mn is 0.2% or less, S is 0.01
It may be about less than or equal to%. Further, addition of a large amount of Mn causes a decrease in saturation magnetic flux density, so the upper limit is made 1%.

As shown in FIGS. 1 and 2, P is required to be added in an amount of 0.02% or more in order to improve the accuracy of the cut surface and the machinability in combination with B as shown in FIGS. However, as shown in FIGS. 1 and 3, if P is excessively added, the cutting surface accuracy and the low temperature toughness are rather deteriorated. Therefore, considering these, the upper limit is made 0.10%.

O forms non-metallic inclusions in steel,
The smaller the content, the better because the magnetic flux density decreases as the content increases, which has an adverse effect on coarsening of crystal grains. Therefore, it is set to 0.006% or less.

N increases the internal stress, and AlN reduces the magnetic flux density in a low magnetic field due to the grain refinement action.
Furthermore, since it becomes BN and inhibits the effect of B, the upper limit is 0.
It is necessary to set it to 004%.

H reduces the magnetic properties and hinders the reduction of void defects, so it is made 0.0002% or less.

In order for B to exert the effect of B mentioned above,
It is necessary to add B in an amount of 0.0003% or more, but the effect does not change even if added in excess, so the upper limit is made 0.005%.

Next, the manufacturing method will be described. Regarding the rolling condition, first, the heating temperature before rolling is set to 1100 ° C. or lower because when AlN is completely dissolved, BN is formed and the effect of B is impaired. However, 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 for eliminating void defects described below increases, so 950 ° C is set as the lower limit.

In hot rolling, the above-mentioned void defects are always generated in the solidification process of steel, although they are large and small, and the means for eliminating them must be done by rolling, so the role of hot rolling is important. . 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 preferable for the magnetic properties to perform a high shape ratio rolling including one or more rolling passes with a rolling shape ratio A of 0.6 or more at 800 ° C. or more to make the size of void defects 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. 80 here
The reason why the high shape ratio rolling is performed at 0 ° C. or higher is that the deformation resistance is large at a low temperature of less than 800 ° C. and the reduction is difficult in ordinary rolling.

Next, in the temperature range of 700 ° C. or more and 900 ° C. or less, the cumulative rolling reduction is made more than 35% to make the crystal grains finer and introduce a strain, and promote recrystallization during the subsequent heat treatment. Furthermore, by this rolling, [10
0] to obtain a texture in which the crystal orientation is aligned parallel to the rolled surface. 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 rolling reduction is set to more than 35% and 70% or less.

Next, following hot rolling, grain coarsening, internal strain removal, 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, 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 the temperature is 600 to 750 ° C. As the dehydrogenation time, various examination results [0.6 (t-50) +
6] Time (t: plate thickness) is appropriate.

The control of the heat treatment temperature is an important factor for effectively utilizing the grain coarsening and the effect of B. Heat treatment at 900 ° C. or higher is necessary to coarsen the crystal grains from the ferrite grain size number 0 to the number −2. However, if the temperature is 1050 ° C or higher, the effect of B is significantly reduced, so the annealing or normalizing temperature is limited to 900 to 1050 ° C. Hydrogen having a plate thickness of less than 50 mm easily diffuses hydrogen, and thus dehydrogenation heat treatment is not necessary and only the above-mentioned annealing or normalization is required.

[0031]

EXAMPLES Next, examples of the present invention will be described together with comparative examples. Table 1 shows the steel composition of the present invention, Table 2 shows the steel composition of the comparative example, and Table 3 (invention) and Table 4 (comparative example) show the manufacturing conditions of the electromagnetic thick plate, the ferrite grain size, and the low magnetic field (magnetization). Power 80A /
The evaluation of the magnetic flux density in a high magnetic field (magnetizing force of 30,000 A / m), the tensile strength, the low temperature toughness, and the machinability and the finish accuracy of the cutting surface is shown as a reflection of the magnetic flux density in m) and the saturation magnetic flux density.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

Sample No. Nos. 1 to 11 are examples of the present invention. 12 to 26 are comparative examples. In the example, the plate thickness is 1
It shows the one finished to 0 to 100 mm, all have high magnetic flux density in low magnetic field and high magnetic field, Charpy absorbed energy value of 40 J or more at -40 ° C, and machinability and cutting surface accuracy are also very high. It is good. On the contrary
No. Since No. 12 has a high C, the magnetic flux density in a low magnetic field is low, and the low temperature toughness is also low. No. 13 has a low magnetic flux density because both Si and Al are low. No. No. 14 has a low-temperature toughness because the sum of Si and Al weight% exceeds 1.5%. No. Since No. 15 has a low P, the machinability and the accuracy of the finished surface are poor. No. In No. 16, since P exceeds the upper limit, low-temperature toughness and cutting surface accuracy are poor. No. No. 17 has a high Mn but a high S, and thus has a low magnetic flux density. No. In No. 18, since N is high, the magnetic flux density is low. No. 19, No. No B is added to any of Nos. 20 and, therefore, low temperature toughness and cutting surface accuracy are poor. No. In No. 21, since H exceeds the upper limit, the magnetic flux density is low and the low temperature toughness is also low. No. In No. 22, the heating temperature exceeds the upper limit and the magnetic flux density and the low temperature toughness are low. No. 23 is 700
The cumulative rolling reduction at ˜900 ° C. falls below the lower limit, and the magnetic flux density is low. No. No. 24, the maximum shape ratio is below the lower limit, and No. In No. 25, the heat treatment temperature is out of the lower limit, so that the magnetic flux density is low.
No. In No. 26, the heat treatment temperature deviates from the upper limit, and the low temperature toughness and cutting surface finish accuracy are poor.

[0037]

As described in detail above, according to the present invention, the strength required for a structural material, the low temperature toughness, the machinability and the finishing accuracy of the cutting surface are combined by a suitable component limitation and a manufacturing method, and a high magnetic property is obtained. The present invention provides a method for economically manufacturing a structural steel material having a shielding property, and has a great industrial effect.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of B and P amounts on the accuracy of a finished surface.

FIG. 2 is a graph showing the effects of B and P amounts on machinability.

FIG. 3 is a graph showing the effects of B and P contents on low temperature toughness.

Claims (4)

[Claims] 1. C .: 0.008% or less, Si: 0.20% or more, less than 1.5%, and Al: 0.
Includes one or both of 10% or more and less than 1.5%, and Si + Al is less than 1.5%, Mn: more than 0.2%, 1.0% or less, P: more than 0.02%. , 0.10% or less, S: 0.005% or less, N: 0.004% or less, O: 0.006% or less, H: 0.0002% or less, B: 0.0003% or more, 0.005 % Or less, a steel slab or a slab having a steel composition consisting of the balance iron and unavoidable impurities is heated to 950 to 1100 ° C., and a rolling pass at which the rolling shape ratio A defined by the following formula becomes 0.6 or more at 800 ° C. or more. Rolling is performed once or more, and then the cumulative rolling reduction is more than 35% and 70% in the temperature range of 700 ° C to 900 ° C.
A method for producing an electromagnetic thick plate for a magnetic shield structure, which comprises performing the following rolling to reduce the plate thickness to less than 50 mm, and then annealing or normalizing at 900 to 1050 ° C. [Equation 1] 2. In% by weight, C: 0.008% or less, Si: 0.20% or more, less than 1.5%, and Al: 0.
Includes one or both of 10% or more and less than 1.5%, and Si + Al is less than 1.5%, Mn: more than 0.2%, 1.0% or less, P: more than 0.02%. , 0.10% or less, S: 0.005% or less, N: 0.004% or less, O: 0.006% or less, H: 0.0002% or less, B: 0.0003% or more, 0.005 % Or less, a steel piece or a steel slab having a steel composition consisting of the balance iron and unavoidable impurities is heated to 950 to 1100 ° C., and a rolling pass at which the rolling shape ratio A defined in the following formula is 0.6 or more at 800 ° C. or more. Rolling is performed once or more, and then the cumulative rolling reduction is more than 35% and 70% in the temperature range of 700 ° C to 900 ° C.
For a magnetic shield structure characterized by performing the following rolling to make a thick plate having a thickness of 50 mm or more, then performing a dehydrogenation heat treatment at 600 to 750 ° C., and then annealing or normalizing at 900 to 1050 ° C. Manufacturing method of electromagnetic plate. [Equation 2] 3. In% by weight, C: 0.008% or less, Si: 0.20% or more, less than 1.5%, and Al: 0.
One or both of 10% or more and less than 1.5% and Si + Al less than 1.5%, Mn: 0.2% or less, P: more than 0.02% and 0.10% or less, S: 0.01% or less, N: 0.004% or less, O: 0.006% or less, H: 0.0002% or less, B: 0.0003% or more, 0.005% or less, residual iron and unavoidable A steel slab or a slab having a steel composition containing impurities is heated to 950 to 1100 ° C., and rolling is performed at 800 ° C. or more at least one rolling pass at which the rolling shape ratio A defined by the following formula is 0.6 or more. Conducted continuously, and in the temperature range of 700 ° C to 900 ° C, the cumulative rolling reduction is more than 35% and 70%.
A method for producing an electromagnetic thick plate for a magnetic shield structure, which comprises performing the following rolling to reduce the plate thickness to less than 50 mm, and then annealing or normalizing at 900 to 1050 ° C. [Equation 3] 4. In% by weight, C: 0.008% or less, Si: 0.20% or more, less than 1.5%, and Al: 0.
One or both of 10% or more and less than 1.5% and Si + Al less than 1.5%, Mn: 0.2% or less, P: more than 0.02% and 0.10% or less, S: 0.01% or less, N: 0.004% or less, O: 0.006% or less, H: 0.0002% or less, B: 0.0003% or more, 0.005% or less, residual iron and unavoidable A steel slab or a slab having a steel composition made of impurities is heated to 950 to 1100 ° C., and rolling is performed at 800 ° C. or more at least one rolling pass at which the rolling shape ratio A defined by the following formula is 0.6 or more. Conducted continuously, and in the temperature range of 700 ° C to 900 ° C, the cumulative rolling reduction is more than 35% and 70%.
For a magnetic shield structure characterized by performing the following rolling to make a thick plate having a thickness of 50 mm or more, then performing dehydrogenation heat treatment at 600 to 750 ° C., and then annealing or normalizing at 900 to 1050 ° C. Manufacturing method of electromagnetic plate. [Equation 4]