JPH0375314A - Production of thick nonoriented silicon steel plate having high magnetic flux density - Google Patents

Abstract

PURPOSE:To obtain a thick nonoriented silicon steel plate having high magnetic flux density in a low magnetic field by specifying the composition of a thick steel plate, rolling conditions, and annealing conditions, performing hot rolling, and then carrying out crystalline grain regulation and dehydrogenating heat treatment. CONSTITUTION:A steel slab or a cast slab having a steel composition consisting of, by weight, <=0.01% C, 0.10-3.5% Si, <=0.20% Mn, <=0.010% S, <=0.05% Cr, <=0.01% Mo, <=0.01% Cu, 0.10-3.0% Al, <=0.004% N, <=0.005% O, <=0.0002% H, and the balance essentially iron is used. The above steel slab or cast slab is heated up to 1150-1300 deg.C and subjected to high shape ratio rolling where rolling pass at >=0.7 rolling shape ratio A is exerted at least once or more under the condition of >=900 deg.C finishing temp., and further, in the case of a thick plate of >=50mm plate thickness, dehydrogenating heat treatment is exerted at 600-750 deg.C., then, annealing is carried out at 750-950 deg.C, if necessary, and in the case of <50mm plate thickness, annealing is performed at 750-950 deg.C. In an equation, A, h1, H0, and R represent rolling shape ratio, entry thickness (mm), exit thickness (mm), and the diameter (mm) of a roll for rolling, respectively.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to the production of electromagnetic thick steel plates with high magnetic flux density for the iron core of magnets used under DC magnetization conditions or for magnetic shields required to shield magnetic fields. This relates to a manufacturing method.

(Prior Art) In recent years, with advances in elementary particle research and medical equipment, which are cutting-edge science and technology, devices that use magnetism are being used in large structures, and there is a demand for improved performance.

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 plates as electromagnetic steel sheets 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, there has been a strong demand for the development of steel materials with even better magnetic properties, particularly those with higher magnetic flux density at low magnetic fields, for example, 80 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/rn.

(Problems to be Solved by the Invention) The purpose of the present invention has been made in view of the above points. The purpose of this invention is to provide a method for manufacturing the same.

(Means for Solving the Problems) In order to achieve such objects, the present invention is constructed as follows.

1. In weight%, C: 0.01% or less, SI: 0. l
O~3.5%, Mn: 0.20% or less, S: 0.01
0% or less, Cr: o, 05% or less, Mo: 0,
01% or less, Cu: 0.01% or less, Ag: 0, lO~
3.0%, N: 0.004% or less, O: 0.005%
Hereinafter, a steel billet or slab having a steel composition consisting of H: 0.0002% or less and the remainder substantially iron is heated to 1150 to 1800°C, and the rolling shape ratio A is set at a finishing temperature of 900°C or higher. 6 for thick plates with a thickness of 5hm or more after performing high shape ratio rolling that takes one or more rolling passes of 0.7 or more.
Magnetic field 8 characterized by performing dehydrogenation heat treatment at 00 to 750°C, then annealing at 750 to 950°C as necessary, and annealing at 750 to 950°C for plate thicknesses less than 50°C.
A method for manufacturing a non-oriented electromagnetic thick plate having a magnetic property with a magnetic flux density of 1.0 Tesla or more at 0 A/m and a high magnetic flux density in a low magnetic field.

However, A- (February stone shoulder-] Yumigo) / (hr + h.)
A: Rolling shape ratio hI: Inlet side plate thickness (ml) h: Outlet side plate thickness (am) R: Roll radius (am) 2, in weight%, c: 0.0196 or less, Si: 0.
lO~3.5%, Mn: 0.20% or less, S: 0.0
10% or less, Cr: 0.05% or less, Mo: 0.01%
Below, Cu: 0.01% or less, Ag: 0.10 to 3.0
%, N: 0.004! ? 6 or less, O: 0.005% or less, H: 0.0002% or less, and the remainder substantially consists of iron. A steel slab or slab is heated to 1150 to 1300°C, and the finishing temperature is 900°C or higher. After performing high shape ratio rolling in which rolling passes with a rolling shape ratio A of 0.7 or more are performed at least once under the following conditions, thick plates with a thickness of 50 mm or more are subjected to dehydrogenation heat treatment at 600 to 750°C. After that, it is normalized at 910 to 1000°C as necessary, and for plate thicknesses of less than 50 mm, it is normalized at 910 to 1000°C. The magnetic flux density at a magnetic field of 80 A/m is 1.0 Tesla. A method for manufacturing a non-oriented electromagnetic thick plate having the above magnetic properties and high magnetic flux density in a low magnetic field.

However, A-(2IF 7:17)/(hl h.)A
: Rolling shape ratio hl: Inlet plate thickness (Ilm) h : Outlet plate thickness (Ilm) R = Roll radius (am) (Function) First, we will describe the magnetization process to increase the magnetic flux density in a low magnetic field. When demagnetized steel is placed in a magnetic field and the 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 as a manufacturing method, the heating temperature was changed. It has been found that it is effective to coarsen the austenite grains by heating as much as possible, to make the rolling finishing temperature as high as possible, to prevent grain refinement due to rolling, and to perform annealing after rolling.

As an elemental influence for reducing internal stress, a reduction in C is necessary. 1 shown in Figure 1. (is f-0,1Mn
-2, As the C content increases in OAN steel, the lower magnetic field (
The magnetic flux density at 80 A/m) has decreased.

In addition, as a result of various studies on the effects of void defects,
It has been found that when the size is 100 μm or more, the magnetic properties are significantly deteriorated.

It has 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.

However, A-(2R(h,-h))/(h,+ho)1
0 A: Rolling shape ratio hI: Inlet side plate thickness (m11) h: Outlet side plate thickness (m11) R: Roll radius (+n) Furthermore, the presence of hydrogen in steel is also harmful as shown in Figure 2, and dehydration It was found that the magnetic properties were significantly improved by performing elementary heat treatment. 0.007 as shown in Figure 2
In C-1,5Si-0,1Mn steel, the size of void defects is reduced to 100μ or less by high shape ratio rolling, and
It can be seen that by reducing the hydrogen in the steel through dehydrogenation heat treatment, the magnetic flux density in a low magnetic field 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.

Regarding the component elements, it has been found that in this manufacturing method, in particular, addition of Si and Al is very effective for obtaining high magnetic flux density in a low magnetic field. Figures 3 and 4 are 0.00
This figure shows the influence of S1 amount and A11k on the magnetic flux density in a low magnetic field (8 [IA/m) in 5C-0, O8Mn steel.

In this manufacturing method, the amount of Si is 0.1 to 3.5%, especially 0.
．． In the range of 6 to 2.5%, the amount of AI is 0.1 to 3.0%,
In particular, high magnetic flux density is shown in the range of 0.9 to 2.5%.

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.

51. Al is an element that is advantageous to add from the viewpoint of magnetic flux density in a low magnetic field, and as shown in Fig. 3, St is in the range of 0.1 to 3.5%, preferably 0. B is added in a range of 2.5%. Further, from FIG. 4, Afi is added in a range of 0.1 to 3.0%, preferably in a range of 0.69 to 2.5%.

The lower the 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. In this sense, Mn is limited to 0420% or less. M
Regarding n, from the point of view of forming MnS-based inclusions, it is more preferably 0.10% or less.

S,0 forms non-metallic inclusions in steel and segregates, thereby hindering the movement of domain walls, and as the content increases, a decrease in magnetic flux density is seen, deteriorating magnetic properties, so it is rare. Moderate. Therefore, S is 0.0
10% or less, and O was 0.005% or less.

Cr, Mo, and Cu reduce the magnetic flux density in a low magnetic field, so it is preferable to have as little as possible, and in order to reduce the degree of segregation, it is necessary to keep them as low as possible. From this point of view, C' is 0.05% or less, Mo is 0.01% or less, Cu is 0.0
1% or less.

The upper limit is 0 because N increases the internal stress and reduces the magnetic flux density in a low magnetic field due to the crystal grain refinement effect of ANN.
．． 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 shelf heating temperature before rolling was set to 1150℃.
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, during hot rolling, the above-mentioned void defects always occur in the solidification process of steel, although they may vary in size, and the means to eliminate these defects must be through rolling, so the role of hot rolling is important. That is, hot rolling is effective in that the amount of deformation per hot rolling is increased and the deformation extends to the center of the sheet thickness.

Specifically, it is good for electromagnetic properties to perform high shape ratio rolling including one or more rolling passes with a rolling shape ratio A of 0.7 or more and to reduce the size of void defects to 100 μm or less. 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, hot rolling is followed by grain coarsening, internal strain removal, and dehydrogenation heat treatment for thick materials with a plate thickness of 50 mm or more. If the plate thickness is 50 mm or more, it is difficult for hydrogen to diffuse, which causes void defects, and combined with the action of hydrogen itself, reduces 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;
Since transformation begins partially at temperatures above 600 to 750°C.

As a result of various studies, the dehydrogenation time (0.8(t -5
0)+6) time (t; plate thickness) is appropriate.

Annealing is performed to coarsen grains and remove internal strain, but
At temperatures below 50°C, crystal grain coarsening does not occur;
At temperatures above ℃, homogeneity of crystal grains in the thickness direction cannot be maintained.
The annealing temperature is limited to 750 to 950°C.

Normalization is performed to adjust grains in the thickness direction of the plate and remove internal strain, but at a temperature of 910°C or higher, which is the A ca point, and too.

At temperatures above ℃, the homogeneity of the crystal grains in the thickness direction cannot be maintained.
The normalization temperature is limited to 910 to 1000°C. In addition, board 1
It is possible to perform this annealing or normalization by dehydrogenation heat treatment performed on a thick material of 150 m or more.

(Example) Table 1 shows the manufacturing conditions, ferrite grain size, and magnetic flux density in a low magnetic field for the electromagnetic thick plate.

Examples 1 to 10 show examples of the present invention, and Examples 11 to 30 show comparative examples.

Examples 1 to 5 were finished to a thickness of 10 h, and exhibited uniform, coarse grains and high magnetic properties. Compared to Example 1, Example 2 has lower C, Examples 3 and 4 have lower Mn, and Example 5 has lower Afl, and exhibits higher magnetic properties. Examples 6-8 are 500mm, Example 9 is 40mm
Example 1O is finished to 10 mm and exhibits uniform, coarse grains and high magnetic properties.

Example 11 has high C, Example 12 has low Si, and Example 13 has high Si.
is high, Example 14 is high in Mn, Example 15 is high in S, Example 1
B is high in Cr, Example 17 is high in Mo, Example 18 is high in Cu, Example I9 is low in l, Example 20 is high in AN), Example 2
1 has high N, Example 22 has high O, Example 23 has high H,
Each exceeds the upper limit, resulting in a low magnetic property value.

In Example 24, the heating temperature was outside the lower limit, in Example 25, the rolling finishing temperature was outside the lower limit, in Example 2B, the maximum shape ratio was outside the lower limit, in Example 27, the dehydrogenation heat treatment temperature was outside the lower limit, and in Example 28.
In Example 29, the annealing temperature exceeds the upper limit; in Example 30, the annealing temperature exceeds the upper limit; and in Example 30, there is no dehydrogenation heat treatment, resulting in low magnetic property values.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to successfully provide a thick steel plate with uniform high electromagnetic properties by appropriately limiting the ingredients, and to utilize the magnetic properties caused by direct current magnetization. It can be applied to structures, and its manufacturing method simultaneously performs the above-mentioned ingredient restriction, grain adjustment after hot rolling, and dehydrogenation heat treatment, providing an extremely economical manufacturing method. This has great industrial effects.

[Brief explanation of drawings]

Figure 1 is a graph showing the influence of C content on magnetic flux density at 80 A/m, Figure 2 is a graph showing the influence of void defect size and dehydrogenation heat treatment on magnetic flux density at 80 A/m; FIG. 3 is a graph showing the effect of 5iii on the magnetic flux density at 80 A/m, and FIG. 4 is a graph showing the effect of the amount of Ag on the magnetic flux density at 80 A/m. Agent Patent Attorney Tadashi Chanoki Youngest brother 1 Figure 3 θ θO2 04 C(ri) θO6 Q8 Figure 2 Figure 4 Sora Suzaku size of defect "0suAAt (%)

Claims (1)

[Claims] 1. In weight%, C: 0.01% or less, Si: 0.10 to 3.5%, Mn: 0.20% or less, S: 0.010% or less, Cr: 0 .05% or less, Mo: 0.01% or less, Cu: 0.01% or less, Al: 0.10 to 3.0%, N: 0.004% or less, O: 0.005% or less, H: 0.0002% or less, the remainder being substantially iron.11
After performing high shape ratio rolling in which the plate is heated to 50 to 1300°C and the finishing temperature is 900°C or more and one or more rolling passes with rolling shape ratio A of 0.7 or more are performed, the plate thickness is 50 mm.
For the above thick plates, after dehydrogenation heat treatment at 600-750°C, annealing at 750-950°C as necessary,
For plates with a thickness of less than 50 mm, the magnetic flux density at a magnetic field of 80 A/m is 1.
A method for manufacturing a non-oriented electromagnetic thick plate with a high magnetic flux density and a magnetic property of 0 Tesla or more. 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) 2. For thick plates with a plate thickness of 50 mm or more after high shape ratio rolling After dehydrogenation heat treatment at 600 to 750°C, normalize at 910 to 1000°C as necessary to obtain a plate with a thickness of 50°C.
The non-directional electromagnetic thickness having a high magnetic flux density and having a magnetic property having a magnetic flux density of 1.0 Tesla or more in a magnetic field of 80 A/m according to claim 1, wherein the non-directional electromagnetic thickness is normalized at 910 to 1000 °C for less than mm. Method of manufacturing the board.