JP3021736B2 - Electromagnetic material and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft magnetic material for various electromagnets based on pure iron deoxidized with magnesium (Mg) and a method for producing the same.

[0002]

2. Description of the Related Art A pure iron thick steel sheet used as a soft magnetic material for various electromagnets or the like has as few impurities as possible other than iron as well as to facilitate movement of a domain wall forming a magnetic domain and to secure good magnetic properties. There is a need to reduce the oxygen that forms inclusions in the steel and to increase the grain size of the steel.

[0003] The obstacles to the movement of the domain wall are inclusions formed in the steel. That is, the domain walls are prevented from moving by the inclusions, so that these must be reduced as much as possible. Inclusions include carbides, oxides and nitrides that precipitate in the crystal.Carbon and nitrogen can be reduced during steel refining and vacuum degassing, but oxygen is reduced to carbon in pure iron-based steel. Since the content is small, the residual amount is large even after vacuum treatment.

In order to reduce this oxygen, it is generally effective to add aluminum (Al) which is a strong deoxidizing material. However, Al contains fine compounds (oxides, nitrides) in steel.
And acts to hinder the movement of the domain wall and to refine the crystal grains, which deteriorates the magnetic characteristics. Therefore, low oxygen and low Al could not be simultaneously satisfied.

[0005]

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide an electromagnetic material which simultaneously satisfies low oxygen and low Al and has excellent magnetic properties and a method for producing the same.

[0006]

In order to achieve the above object, the present invention has the following constitution. (1) In terms of weight%, C: 0.005% or less, Si: 0.02% or less, Mn: 0.15% or less, P: 0.015% or less, S: 0.003% or less, Al : 0.01% or less, N: 0.005% or less, Mg: 0.001 to 0.015
%, And the balance being substantially Fe, and (2) vacuum degassing the molten steel refined in a steelmaking furnace to obtain C:
After decarburizing to 0.005% by weight or less, a Mg component is supplied to the molten steel so that the total amount of Mg in the molten steel is 0.001 to 0.015.
%, Which is deoxidized so as to be contained in the range of 0.1%, then cast, and then subjected to hot rolling and heat treatment. In the present invention,
It is preferable to supply the Mg component in a non-oxidizing atmosphere.

Hereinafter, the present invention will be described in detail. In the method for producing an electromagnetic material according to the present invention, low carbon molten steel refined in a steelmaking furnace such as a converter or an electric furnace is subjected to vacuum degassing to reduce the carbon content to 0.005% or less. This molten steel is stored in a container such as a ladle, and if necessary, is subjected to dephosphorization and desulfurization treatment, and is supplied with magnesium to perform deoxidation.

[0008] Mg has a low solubility in the molten iron and has a high vapor pressure at the temperature of the molten steel, so that it hardly remains in the steel, so that it has no effect as an alloy. I can't. In the present invention, an appropriate amount of Mg component is added so as to remain and deoxidized, and deoxidation with Al is hardly performed, or even if it is performed, it is minimized, and a low oxygen material suitable as a soft magnetic material is used. obtain. FIG.
Shows the effect of the Mg content in the electromagnetic thick plate on the magnetic flux density in a magnetic field of 80 A / M.
It can be seen that when g is less than 0.001% or more than 0.015%, the magnetic flux density rapidly deteriorates. The Mg content is preferably 1.5 times or less the oxygen content, thereby completely fixing oxygen harmful to the magnetic properties of the soft magnetic material,
Although it can be rendered harmless by finely dispersing it in the form of an oxide, if it is contained in an excessively large amount, the residual amount of the oxide decreases, and the magnetic properties deteriorate.

In order to supply Mg, a ladle, a tundish, a continuous casting mold, or a steel ingot may be supplied by blowing metal Mg (granules, flakes, etc.), charging with a wire, or charging as briquettes with iron. This is performed in the molten steel charged in any of the casting molds and the like. M as described above
g hardly remains in the molten steel, that is, since its yield is low, it is good to add it to a deep position of the molten steel in order to maximize the utilization efficiency. 0.05% addition rate to avoid
/ Min or less is preferable. In addition, it is necessary to make the atmosphere non-oxidizing in order to reduce the oxidizing property of the slag existing on the steel bath surface. In order to prevent this, it is desirable to suppress the flow of the atmosphere.

As described above, in the present invention, deoxidation of Al is suppressed by using Mg, and deterioration of magnetic characteristics due to minimizing the amount of Al added is prevented. FIG.
It shows the relationship between the Al content and the magnetic flux density at a magnetic field of 80 A / M. From this figure, it can be seen that when the Al content is 0.01% or more, the magnetic flux density is significantly deteriorated. That is, if the amount of addition increases, the inclusions such as AlN precipitated in the steel disperse in large amounts, so that the movement of the domain wall is easily hindered, and the deterioration of magnetism is promoted. Therefore, it should be 0.01% or less, preferably 0.005% or less.

[0011] The molten steel thus treated is subjected to hot rolling after adjusting the components as necessary. Hot rolling has no special conditions,
It is preferable to carry out the molding by a usual method to form a thick plate, and further to anneal at 600 to 800 ° C. in order to grow crystal grains and remove distortion.

The reasons for limiting the components of the material of the present invention will be described below. C forms carbides in the steel and hinders the movement of the domain wall. Therefore, the smaller the better, the better, but up to 0.005% is allowed to maintain a certain strength. Since Si generates scale during slab heating or hot rolling and deteriorates surface properties, the lower the better, the better the 0.02% is set as the allowable limit. Mn is usually added as a deoxidizer like Si,
In the present invention, since Mg deoxidation is mainly performed, the effect of Mn is not expected. However, the solid solution S during slab heating is fixed,
Although it has the effect of preventing red heat embrittlement, it can be contained up to 0.15%. It is better that P and S are small as impurities. Particularly, S is preferable to be small in order to precipitate MnS and FeS and adversely affect magnetism. Therefore, P is set to 0.015% or less and S is set to 0.003% or less. Since Al precipitates inclusions such as AlN and suppresses the growth of crystal grains and deteriorates magnetism as described above, the Al content is preferably as small as possible, and is preferably 0.01% or less, preferably 0.005% or less. .

When N is contained in an amount exceeding 0.005%, A
The precipitation amount of 1N increases. Therefore, the smaller the better.

Mg is a characteristic feature of the present invention. As described above, Mg is deoxidized to suppress deoxidation by Al which is harmful to magnetism. Since Mg has a high vapor pressure, it is difficult to yield into steel. However, it is preferable to improve the charging method so that the content of Mg is 1.5 times or less of oxygen and is contained in the range of 0.001 to 0.015%. Can be obtained. Hereinafter, the present invention will be described based on examples.

[0015]

EXAMPLE A 250 ton top-bottom blow converter and an RH degassing device are used to melt ultra-low carbon steel from a pretreated hot metal that has been dephosphorized and desulfurized. It was melted. At the end of the RH treatment, 150 kg of Al was added into the degassing tank to perform preliminary deoxidation. After draining the slag on the ladle, 800 kg of quicklime was added, and an iron-coated wire containing 10% of Mg was provided from the ladle for 15 minutes to perform deoxidation with Mg. After that, it is continuously cast to a thickness of 250
mm slabs were produced. On the other hand, a slab according to a conventional method in which the amount of Al added was 300 kg and Mg deoxidation was not performed was manufactured as a comparative example.

Table 1 shows the chemical composition of each slab.

[0017]

[Table 1]

After heating these slabs to a temperature of 1200 ° C., they are rolled into a thick plate having a thickness of 60 mm.
After normalizing for 4 hours at 50 ° C., the furnace was cooled.

A part of the plate was cut out, and the magnetic flux density in the L direction was measured. The applied magnetic field at the time of measurement is 80 A / M. The magnetic flux density was 1.33T for the steel of the present invention and 1.17T for the comparative steel.

[0020]

As described above, according to the present invention, the use of aluminum is suppressed as much as possible, and by applying deoxidation with magnesium, a pure iron-based thick plate having excellent electromagnetic characteristics can be easily manufactured. .

[Brief description of the drawings]

FIG. 1 is a diagram showing the effect of Mg content on magnetic flux density in a magnetic field of 80 A / M.

FIG. 2 is a diagram showing a relationship between an Al content and a magnetic flux density at a magnetic field of 80 A / M.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 38/00 C21C ⁷ /00-7/10

Claims (3)

(57) [Claims] 1. As weight%, C: 0.005% or less, Si: 0.02% or less, Mn: 0.15% or less, P: 0.015% or less, S: 0.003% or less, Al : 0.01% or less, N: 0.005% or less, Mg: 0.001 to 0.015%, and the balance is substantially Fe. 2. The molten steel refined in a steelmaking furnace is degassed by vacuum degassing to a C content of 0.005% by weight or less, and then a Mg component is supplied to the molten steel to reduce the total Mg content in the molten steel to 0%. .001-
A method for producing an electromagnetic material, comprising deoxidizing so as to be contained in a range of 0.015%, then casting, followed by hot rolling and heat treatment. 3. The method according to claim 2, wherein the Mg component is supplied in a non-oxidizing atmosphere.