JPH04333517A - Production of thick nonoriented silicon steel plate excellent in magnetic property - Google Patents

Abstract

PURPOSE:To obtain the silicon steel plate having high strength by heating a slab or cast slab of a steel, having a composition in which respective upper limits of C, Si, Mn, S, Al, N, O, and H are limited, up to a specific temp. and subjecting the above-mentioned slab or cast slab to rollings, in succession, under respectively specified conditions at temps. not lower than and not higher than a specific temp., respectively. CONSTITUTION:A slab or cast slab of a steel having a composition consisting of, by weight, <=0.01% C, <=0.02% Si, <=0.20% Mn, <=0.010% S, <=0.040% Al, <=0.004% N, =0.005% O, <=0.0002% H, and the balance iron is prepared. This slab or cast slab is heated to 950-1150 deg.C and subjected to rolling where rolling pass of >=0.6 rolling shape ratio A represented by an equation is done at least once at >=800 deg.C, by which harmful vacancy defects are removed and deterioration in magnetic properties is prevented. Successively, rolling is done at <=800 deg.C at 35-70% reduction of area and the [100] crystal orientation is made random in a direction parallel to the rolling direction, by which magnetic properties in a medium magnetic field can be remarkably improved and high strength can be obtained. In the above equation, hi, ho, and R represent inlet plate thickness (mm), outlet plate thickness (mm), and rolling roll radius (mm), respectively.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a method for producing a non-oriented electromagnetic plate having high strength and excellent magnetic properties in a low magnetic field.

0002

BACKGROUND OF THE INVENTION 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. The magnetic pole material and return yoke material for particle accelerators used under DC magnetization conditions have a high saturation magnetic flux density and a high strength of 10 Oe (
A high magnetic flux density in a medium magnetic field (around 800 A/m) is required.

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. but,
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 high strength and excellent magnetic properties have been developed.
In particular, there is a strong demand for the development of steel materials with high magnetic flux density in low magnetic fields, for example around 10 Oe (800 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 the medium magnetic field near 10 Oe.

[0005]

[Problems to be Solved by the Invention] The object of the present invention has been made in view of the above points, and is to provide a method for manufacturing a non-oriented electromagnetic thick plate having high strength and excellent magnetic properties in a medium magnetic field. It is.

[0006]

[Means for Solving the Problems] The present invention provides C:
0.01% or less, Si: 0.02% or less, Mn: 0.2
0% or less, S: 0.010% or less, Al: 0.040%
Below, N: 0.004% or less, O: 0.005% or less,
H: 0.0002% or less, a steel slab or slab having a steel composition consisting essentially of iron, heated to 950 to 1150°C,
High strength characterized by performing rolling at least one rolling pass with a rolling shape ratio A of 0.6 or more at 800°C or higher, followed by rolling at 800°C or lower with a rolling reduction of 35 to 70%. This is a method for producing non-oriented electromagnetic thick plates with excellent magnetic properties in medium magnetic fields.

[0007]

[Math 2]

[0008]

[Operation] Conventionally, in order to obtain a high magnetic flux density in a low magnetic field, it has been an important technique to coarsen crystal grains that impede movement of domain walls (Japanese Patent Application Laid-Open No. 60-96749). On the other hand, there was no knowledge of a method for obtaining high magnetic flux density in a medium magnetic field.

In order to obtain a high magnetic flux density in a medium magnetic field, the inventors believe that the direction of easy magnetization should be aligned with the plate surface, rather than coarsening the crystal grains to make the domain walls easier to move, which was conventionally said. I found out that it is important that they are facing in parallel directions. In other words, they found that the magnetic properties in medium magnetic fields were significantly improved by making the [100] direction random in a direction parallel to the plate surface.

Furthermore, it has been found that in order to obtain high strength, it is important to apply a reduction ratio of at least a certain value in a low temperature region and to produce a product as rolled. As the hot rolling conditions for these, by taking a rolling reduction of 35% to 70% at 800°C or lower, the [100] crystal orientation becomes random parallel to the rolling direction, and at the same time, high strength is obtained. .

FIG. 1 shows 0.006Si-0.07Mn-0
．． It shows the rolling reduction of 018Al steel at 800°C or less and the magnetic flux density at 10Oe. A reduction of 35-70% results in high magnetic flux density. Furthermore, as a means to obtain high magnetic flux density in medium magnetic fields, we conducted detailed studies on the effects of elements and void defects that cause internal stress, and achieved the desired objective. Furthermore, as a result of various studies on the influence of void defects, it was found that those with a size of 100 μm or more significantly deteriorate the magnetic properties. It has been found that in order to eliminate harmful void defects of 100 μm or more, the rolling shape ratio A must be 0.6 or more.

0012

[Math 3]

Furthermore, it has been found that the presence of hydrogen in steel is also harmful, and that magnetic properties can be significantly improved by dehydrogenation heat treatment. By reducing the size of void defects to 100 μm or less through high shape ratio rolling and reducing hydrogen in the steel through dehydrogenation heat treatment, the magnetic flux density in a medium magnetic field increases significantly.

Next, the reason for limiting the ingredients 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, the most, and reducing it as much as possible contributes to not lowering the magnetic flux density in a medium magnetic field. In addition, from the viewpoint of magnetic aging, the lower the content, the less the deterioration over time, and it can be used permanently with good magnetic properties.For this reason, it is limited to 0.01% or less. As shown in FIG. 2, an even higher magnetic flux density can be obtained by reducing the amount to 0.005% or less.

[0015] It is preferable that Si and Mn be small in terms of magnetic flux density in a medium magnetic field, and that Mn should be small in terms of forming MnS-based inclusions. From this meaning, Si is 0.02%
Hereinafter, Mn is limited to 0.20% or less. Regarding Mn, it is more preferable to use 0 since MnS-based inclusions are generated.
．． It is preferably 10% or less.

[0016] S and O form non-metallic inclusions in steel and have a detrimental effect on coarsening of crystal grains, and as their content increases, a decrease in magnetic flux density is observed, degrading magnetic properties, so the less the better. . Therefore, S was set to 0.010% or less, and O was set to 0.005% or less.

[0017] Al is used as a deoxidizing agent, and if it becomes too large, inclusions will form and the properties of the steel will be impaired, so the upper limit is set at 0.040%. Furthermore, in order to reduce AlN, which is a precipitate that prevents crystal grain coarsening, the lower the content, the better, and preferably 0.020% or less.

The upper limit is set to 0.004% because N increases internal stress and AlN reduces the magnetic flux density in a medium magnetic field due to its crystal grain refining effect. H is 0.0002% because it lowers the magnetic properties and prevents the reduction of void defects.
The following shall apply.

Next, the manufacturing method will be described. Regarding the rolling conditions, first of all, the pre-rolling heating temperature should be set to 1150°C or less. At heating temperatures exceeding 1150°C, there will be large variations in the heated γ grain size in the thickness direction, and this variation will remain even after rolling and cause the final result. Since the crystal grains become non-uniform, the upper limit is set to 1150.
℃. If the heating temperature is less than 950°C, the deformation resistance during rolling will increase, and the rolling load with a high shape ratio to eliminate the void defects described below will increase.
is the lower limit.

[0020] Regarding hot rolling, the above-mentioned porous defects may vary in size during the solidification process of steel, but they always occur, and the means to eliminate them must be through rolling, so the role of hot rolling is important. 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, performing high shape ratio rolling including one or more rolling passes with a rolling shape ratio A of 0.6 or more,
Setting the size of the void defects to 100 μm or less is good for magnetic 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.

[0021] Next, by setting the cumulative reduction rate to 35% or more at a temperature of 800°C or less, the [100] crystal orientation is made random parallel to the rolling direction. However, if the rolling reduction exceeds 70%, the grain size after heat treatment becomes non-uniform in the thickness direction, increasing the variation in magnetic flux density. Furthermore, as shown in FIG. 3, high strength can be obtained by setting the cumulative reduction rate to 35% or more at a temperature of 800° C. or less. Therefore, in order to obtain high magnetic properties with high strength and low magnetic field,
The reduction rate is set to 35 to 70%.

[0022]

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

[0023]

[Table 1]

[0024]

[Table 2]

Examples 1 to 8 illustrate embodiments of the invention; Examples 9 to 8 illustrate examples of the invention;
20 shows a comparative example. Examples 1 to 5 were finished to a plate thickness of 75 mm, had high strength, and exhibited high magnetic flux density in a medium magnetic field. Example 1
Compared to the above, Example 2 has lower C, Examples 3 and 4 have lower Mn, and Example 5 has lower Al, showing higher magnetic properties.

Example 6 is 350mm, Example 7 is 40mm, Example 8
is finished to 6mm and has a high magnetic flux density. Example 9 has high C, Example 10 has high Si, Example 11 has high Mn,
Example 12 has high S, Example 13 has high Al, Example 14 has high N, Example 15 has high O, and Example 16 has high H, each of which exceeds the upper limit, resulting in a low magnetic property value. In Example 17, the heating temperature exceeded the upper limit and the magnetic flux density was low. Example 18
Since the heating temperature is outside the lower limit and the maximum shape ratio is small, the magnetic flux density is low. In Example 19, the rolling reduction of 800° C. or less is outside the lower limit, the strength is low, and the magnetic flux density is low. In Example 20, the maximum shape ratio is outside the lower limit and the magnetic flux density is low.

[0027]

[Effects of the Invention] According to the present invention, by appropriately limiting the ingredients, it has been possible to provide a thick steel plate with uniform high electromagnetic properties, making it applicable to structures that utilize magnetic properties due to direct current magnetization. Moreover, the manufacturing method thereof is the above-mentioned limiting of ingredients and hot rolling, which provides an extremely economical manufacturing method and has great industrial effects.

[Brief explanation of drawings]

FIG. 1 is a graph showing the influence of a rolling reduction of 800° C. or less on magnetic flux density at 10 Oe.

FIG. 2 is a graph showing the influence of C content on magnetic flux density at 10 Oe.

FIG. 3 is a graph showing the influence of a rolling reduction of 800° C. or less on tensile strength.

Claims (1)

[Claims] [Claim 1] In weight %, C: 0.01% or less, Si: 0.02% or less, Mn: 0.20% or less, 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, and the remainder is substantially iron.
Heating to 50 to 1150°C, rolling at least once at 800°C or higher with rolling shape ratio A of 0.6 or more, followed by rolling at 800°C or lower with a rolling reduction of 35 to 70%. A method for manufacturing a non-oriented electromagnetic thick plate with high strength and excellent magnetic properties in a medium magnetic field. [Math 1]