JPH066778B2 - Electromagnetic soft iron for thick plates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has excellent magnetic characteristics suitable for blocking leakage magnetism, and mechanical characteristics required as a structural material for a shielded room. And an electromagnetic soft iron for thick plates.

(Prior Art) Along with the remarkable progress of science and technology in recent years, practical application of nuclear energy has progressed, and research on atomic nuclei has been required more and more. The cyclotron is an experimental device used in this research.

This cyclotron uses a huge DC electromagnet to accelerate the ions. Therefore, since a large amount of leakage magnetism is generated during its use, the steel sheet used as the structural member of this cyclotron is required to have magnetic shutoff characteristics and mechanical properties as structural members. ing.

As a steel plate having such magnetic shutoff characteristics, there is an electromagnetic soft steel plate, and thin plates generally used for transformers, iron cores, etc. are well known. These are electromagnetic soft iron bars and electromagnetic soft iron plates that have been conventionally specified as JIS C 2503 or JIS C 2504 as steel materials with excellent magnetic properties. JIS C 2503 is a bar with a diameter of 1.0 to 16 mm, and JIS C 2504 is a thin plate with a thickness of 0.6 to 4.5 mm, both of which are small for relays or electromagnets. It is intended for application to parts.

Although not classified for magnetic use, S10C, which is a carbon steel material for machine structure specified in JIS C 4051, is used for hot working to a width of 250 mm while emphasizing mechanical properties and sacrificing magnetic properties. However, there is an example of using it as a magnetic material.

Further, as disclosed in JP-A-60-96749, JP-B-63-45442 or JP-B-63-45443, Al containing a large amount of sol.Al of 0.005 to 1.00% by weight.
A thick plate for direct current magnetization, which is a deoxidized ultra-low carbon steel, has been proposed and put into practical use in recent years.

(Problems to be Solved by the Invention) However, these known methods have excellent magnetic characteristics such as capable of blocking leakage magnetism during construction and use of a cyclotron, and as a structural member. It is not possible to provide electromagnetic soft iron for thick plates that has the required mechanical properties.

That is, (i) the electromagnetic soft iron bar or electromagnetic soft iron plate shown in JIS C 2503 or JIS C 2504 is intended for small parts as described above, and the mechanical characteristics as structural members are taken into consideration at all. It has not been. Therefore, for example, when applying this electromagnetic soft iron plate to the magnetic shield material of the above-mentioned cyclotron, it is necessary to laminate several tens to several hundred sheets of this electromagnetic soft iron plate in order to secure the strength of the device,
From the viewpoint of manufacturing cost and product quality, practical implementation cannot be achieved. (Ii) In the example using the carbon steel material for mechanical structure shown in JIS G 4051, since no consideration was given to the magnetic properties, the maximum magnetic permeability μ _max (B / H) was a very low value of 1800 or less. Only got it. Therefore, the desired electromagnetic soft iron for thick plates cannot be provided, and it is not suitable for use as a magnetic shield material that requires high magnetic permeability.

Further, (iii) the magnetic steel sheet disclosed in JP-A-60-96749 has a maximum magnetic permeability value of 12850 (B / H) to 4260 (B / H).
The values vary widely, and the values are not sufficient for electromagnetic steel sheets for thick plates. Further, the mechanical properties of this electromagnetic steel sheet are varied, as can be seen from the tensile strength of 26 to 34 kgf / mm ^2, and are not applicable as electromagnetic steel sheets for thick plates.

Further, (iv) Japanese Patent Publication No. 63-45442 or Japanese Patent Publication No. 63-43442.
Although the method disclosed in -45443 publication is a method capable of increasing the maximum magnetic permeability to about 2000 to 5000,
Considering, for example, the case where the electromagnetic steel sheet obtained by this method is applied to the above-mentioned cyclotron, it cannot be said to be a sufficient value, and further improvement is desired.

As described above, in these known means, for example, as a steel plate used for a magnetic shield material of a cyclotron, an electromagnetic soft iron for a thick plate having excellent magnetic properties and having mechanical properties required as a structural member is provided. I couldn't get it.

An object of the present invention is to provide an electromagnetic soft iron for thick plates, which has excellent magnetic properties suitable for blocking leakage magnetism and mechanical properties required for structural members.

(Means for Solving the Problems) The inventors of the present invention have conducted various studies in order to solve the above problems, and as a result, as disclosed in JP-A-60-96749, a material for electromagnetic soft iron for thick plates. By using not only Al deoxidized ultra low carbon steel as the above, but using Al deoxidized ultra low carbon steel with an appropriate amount of Si added, it has extremely good magnetic properties and mechanical properties, that is, tensile strength. It was discovered that it is possible to obtain an electromagnetic soft iron for thick plates, which has significantly improved strength and yield strength compared to conventional Al deoxidized electromagnetic soft iron.

That is, the inventors of the present invention have an important point in manufacturing electromagnetic soft iron for thick plates having good magnetic properties that the content of a component that increases the demagnetization rate is reduced as much as possible and that magnetic properties and mechanical properties in the plate thickness direction are reduced. We have found that it is to enhance the homogeneity of the characteristics.

That is, as the component element that increases the first demagnetization rate,
Although there are C, S, Cu, Cr, Al, etc., the present inventors have found that it is effective to limit the content of these elements, particularly Al, to an appropriate amount. In addition, it was also found that Si is mentioned as a component element that enhances tensile strength without reducing magnetic properties, and that magnetic properties and mechanical properties are remarkably improved by adding an appropriate amount of this Si.

Furthermore, in order to ensure the homogeneity of the second magnetic characteristic,
The present inventors have also completed the present invention by finding that it is necessary to reduce the contents of non-metallic inclusion-causing elements and the elements that easily segregate and make the crystal grains as uniform as possible in the plate thickness direction.

Here, the gist of the present invention is an electromagnetic soft iron for thick plates, and in% by weight, C: 0.02% or less, Si: more than 0.50% to 1.00%, Mn: 0.05 or less, P: 0.01% or less. S: 0.01 or less, sol.Al: 0.005 to 0.060%, balance Fe and unavoidable impurities, and electromagnetic soft iron for thick plates with excellent magnetic properties.

(Operation) Hereinafter, the present invention will be described in detail together with operation effects. In this specification, "%" means "% by weight" unless otherwise specified.

First, the reason why the composition of the electromagnetic soft iron for thick plates according to the present invention is limited as described above will be described.

C is an element that most increases the demagnetization rate by its inclusion, and it is desirable to reduce it as much as possible. However, C
Since the reduction of the number of steps requires many steps and leads to an increase in the manufacturing cost, the content is limited to 0.02% or less.

In the present invention, Si is an extremely important element in order to exert the effects of the present invention, and promotes grain size control, improvement of magnetic properties, and further improvement of tensile strength, and removal of Si. Since it also acts as an acid agent, it is necessary to add more than 0.50%. However, if added in too large an amount, the steel becomes brittle and is not suitable as a structural thick plate material. In addition, as the amount of Si added increases, the A ₁ transformation point rises,
The upper limit will be 1.00%, which will raise the optimum heat treatment temperature.
And limit.

Similar to C, it is desirable to reduce Mn from the viewpoint of demagnetization rate, but when it is used as a structural thick plate material, its upper limit is 0.50 in order to secure the necessary minimum strength in addition to magnetic properties. Limit to%.

It is desirable that both P and S are easy to form non-metallic inclusions in the steel and the amount thereof is small, but since reduction of these causes an increase in cost, P is limited to 0.01% or less and S is limited to 0.01% or less.

Al is an extremely important element for exerting the effects of the present invention, and is an element that increases the demagnetization rate. Further, Al is combined with N in steel to form aluminum nitride and mixed grains of steel. It is desirable that the content is small so as to promote the formation.
However, in the present invention, a certain amount of Al must be contained in order for Al to act as a deoxidizing agent, promote the soundness of the internal quality, and cope with the extreme thickening. From this perspective,
The Al content is limited to 0.005% or more and 0.060% or less.

The electromagnetic soft iron for thick plates having the composition according to the present invention,
In addition to the above composition, at least one or more selected from the group consisting of Cr, Mo, Cu and N,
Alternatively, it is more desirable to contain oxygen as shown below. That is, Cr, Mo, Cu, or N is an element that increases the demagnetization rate of the magnetic characteristics, and it is desirable that the content is as small as possible in order to reduce the degree of segregation. However, since Cr, Mo, and Cu are mixed from refractory materials, it is difficult to achieve extreme reduction. Further, N, as described above, combines with Al and promotes grain mixing of steel. Therefore, it is more preferable that Cr is 0.20% or less, Mo is 0.02% or less, Cu is 0.10% or less, or N is 0.01% or less.

Further, oxygen forms a non-metallic inclusion and segregates to hinder the movement of the domain wall, and as the content thereof increases, the coercive force of the steel sheet increases, possibly resulting in deterioration of magnetic properties. Therefore, the smaller the content, the more desirable,
It is more desirable to contain oxygen in an amount of 0.003% or less.

Electromagnetic soft iron for thick plates according to the present invention having such a composition,
It has extremely excellent magnetic properties. That is, the magnetic property is the most important property that electromagnetic soft iron should have, and the maximum magnetic permeability μ _max can be mentioned as a specific index of the magnetic property, but as described above, the rapid progress of chemical technology in recent years. Therefore, high magnetic permeability has been required, and it is desirable to have μ ≧ 7000 (B / H) as the necessary minimum value,
The structural thick electromagnetic soft iron according to the present invention has an extremely high magnetic permeability which easily exceeds this value.

Also, the magnetic flux density when the magnetic field is 10e (oersted) (below
B ₁ ) is also preferably B ₁ ≧ 7000 (B / H) similarly to the maximum magnetic permeability μ _max , but the electromagnetic soft iron for thick plates according to the present invention has an extremely high value exceeding this value. It has a high magnetic flux density.

Furthermore, a method for manufacturing the structural thick electromagnetic steel sheet according to the present invention will be described.

Steel may be melted by either a converter manufacturing method or an electric furnace melting method, and further, if necessary, through a refining process such as ladle refining or vacuum degassing, elements (C, Mo , Cu, N) to the utmost and to minimize the generation and segregation of non-metallic inclusions,
P and S are reduced, and oxygen is removed using Al.

Next, in the hot working step, heating conditions and special work before working are completely unnecessary. Further, the form of processing may be either rolling using a rolling mill or forging pressure using a forging machine, and no limitation is required.

Next, following hot working, heat treatment is performed to adjust the crystal grains, remove working strain, and improve magnetic properties such as magnetic permeability. As such heat treatment, it is most desirable to perform annealing from the viewpoint of ensuring sufficient magnetic properties, and the conditions are (700 to Ac ₃ points) ° C, It is preferable that the time is not less than 900 hours, more preferably 900
℃ × 1 hour.

According to the present invention described in detail above, it is possible to easily and surely provide a structural thick plate electromagnetic soft iron having an extremely excellent magnetic permeability.

Furthermore, although this invention is demonstrated with the Example, this is an illustration of this invention, and this does not limit this invention unfairly.

Example Smelting and melting were performed by an electric furnace melting method to obtain a steel slab having the composition and the plate thickness shown in Table 1.

The obtained steel slab was processed (rolled) into a predetermined shape and then annealed under the conditions shown in Table 1 to obtain Sample No. 1 to Sample No. 34.

For these sample No. 1 to sample No. 34, the magnetic characteristics are the maximum permeability μ _max (B / H) and the magnetic flux density when the magnetic field is 10e.
B ₁ (Gauss), and the mechanical properties, YP (kgf / mm
² ), tensile strength TS (kgf / mm ² ), and V notch Charpy impact test value vE ₀ ^Ave (kgf-m) at 0 ° C. were measured.

The results are shown in Table _1, and graphs showing the influence of the sampling position of the sample in the plate thickness direction, the heat treatment temperature or the plate thickness on B ₁ and TS are shown in FIG. 1, FIG. 2 and FIG. 3, respectively. Show.

In addition, for example, for electromagnetic soft iron for thick plates used as a shield material of a cyclotron, (i) magnetic characteristics: μ _max ≧ 7000, B ₁ ≧ 7000, (ii) mechanical characteristics: TS ≧ 30, vE ₀ ^Ave ≧ 4.8 Are required, and these are used as the criteria for the pass / fail judgment also in this embodiment.

In Table 1, sample No. 1 to sample No. 26 are samples according to the present invention.

Sample No. 1 is a sample relating to the basic composition in this example, Sample No. 2 and Sample No. 3 are heat treatment conditions, and Sample Nos. 16 to 26 are plate thickness and heat treatment conditions. These are the samples when the sample No. 1 is changed.

Further, in contrast to Sample No. 1, Sample No. 4 to Sample No. 7 are samples in which the C content is contained near the upper limit of the range of the present invention, and Sample No. 8 to Sample No. 11 are Si. Sample containing the content near the upper limit of the present invention, Sample No. 12 is a sample containing the Mn content near the upper limit of the present invention, Sample No. 13 is the sol.Al content In the range of the present invention, Sample No. 14 is a sample containing sol.Al content near the upper limit of the range of the present invention, Sample No. 15 is C and Mn in the range of the present invention This is a sample containing up to near the upper limit of.

It is understood that all of Samples 1 to 26 satisfy all the above-mentioned reference values and are extremely suitable as a shield material for a cyclotron, for example.

On the other hand, Sample Nos. 27 to 34 are comparative samples.

In sample No. 27, the sol.Al content is 0.086%, which is beyond the range of the present invention, so it is understood that the magnetic properties are insufficient.

Sample No. 28 has a C content of 0.028%, which exceeds the range of the present invention, and thus it is understood that the magnetic flux density B ₁ is insufficient.

In the sample No. 29, the Si content is 1.57%, which exceeds the range of the present invention, so that it can be seen that the V notch Charpy impact test value vE ₀ ^{Ave at} 0 ° C. is remarkably reduced.

Sample No. 30 has a Si content of 0.008%, which is less than the range of the present invention, so that it is understood that the tensile strength TS is significantly reduced.

Sample No. 31 has a Mn content of 1.17%, which exceeds the range of the present invention, and thus it is understood that the magnetic characteristics are deteriorated.

In sample No. 32, the sol.Al content is 0.089%, which exceeds the range of the present invention, and thus it is understood that the magnetic characteristics are also deteriorated.

Further, although Sample No. 33 and Sample No. 34 are samples in which P and S are beyond the scope of the present invention, the results of the lymprint test and the sulfaprint test performed as one of the internal quality tests,
The segregation of P and S was remarkable and it was unsuitable for use as a steel material.

Further, as is clear from FIG. 1 to FIG. 3, the electromagnetic soft iron for thick plates according to the present invention secures homogeneity of magnetic properties and mechanical properties in the plate thickness direction, heat treatment temperature, It can be seen that it is not affected by other manufacturing conditions such as plate thickness.

(Effects of the Invention) As described in detail above, by using the Al deoxidized plate electric soft iron according to the present invention, a thick plate electromagnetic soft iron having mechanical characteristics and magnetic characteristics suitable for, for example, a cyclotron can be reliably obtained. It is now possible to provide stable and stable.

The practical significance of the present invention having such effects is extremely remarkable.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of the sampling position of the sample in the plate thickness direction on B ₁ and TS in the example of the present invention; FIG. 2 shows the effect on B ₁ and TS in the example of the present invention. FIG. 3 is a graph showing the influence of the heat treatment temperature; and FIG. 3 is a graph showing the influence of the plate thickness on B ₁ and TS in the example of the present invention.

Claims (1)

[Claims] 1. An electromagnetic soft iron for thick plates, which, by weight%, C: 0.02% or less, Si: more than 0.50% to 1.00%, Mn: 0.50% or less, P: 0.01% or less, S: 0.01% or less. , Sol.Al: 0.005-0.060%, electromagnetic soft iron for thick plates with excellent magnetic properties, consisting of balance Fe and unavoidable impurities.