JPH11269617A - Iron-chromium series soft magnetic steel excellent in magnetic property and temperature characteristic at ac - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an Fe-Cr series soft magnetic steel high in the maximum magnetic flux densiy at AC and further small in the temp. dependency of Bm. SOLUTION: This steel is the one having a compsn. contg., by weight, <=0.05% C, <=3.0% Si, <=1.0% Mn, <=0.04% P, <=0.01% S, 5.0 to 18.0% Cr, <=0.05% N, <=4.0% Al and <=0.5% Ti (including the case of no addition), and the balance Fe with inevitable impurities and also satisfying 40<=4.3 (weight % Cr)+15.1 (weight % Al)+19.1 (weight % Si)+9.8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Fe--Cr soft magnetic steel used for a motor yoke, a core of an electromagnetic flowmeter, and the like.

[0002]

2. Description of the Related Art Conventionally, SEC (Zn plated steel sheet), SUYP (Electromagnetic soft iron) have been used for motor yoke and electromagnetic flowmeter core.
Fe-based soft magnetic materials such as these are used.

[0003]

In recent years, there has been an increasing demand for high-speed rotation of motors. In order to rotate the motor at high speed, it is necessary to increase the driving frequency. In order to obtain a high motor torque in a high frequency region, it is essential that the yoke material has a high magnetic flux density.

On the other hand, an electromagnetic flowmeter is a device that generates a magnetic field B in the vertical direction of a fluid flowing at a speed v, measures an output voltage generated according to Faraday's law of electromagnetic induction, and measures the flow rate of the fluid. . The core of the flow meter has the effect of increasing the output voltage by increasing the magnetic field B and facilitating flow rate measurement. Generally, the current for generating the magnetic field B is 50
Hz or 60Hz alternating current.

In recent years, there has been a strong demand for electromagnetic flowmeters to improve the accuracy of flow measurement. In order to improve the accuracy of the flow rate measurement, it is necessary to increase the frequency of the current for generating the magnetic field in order to prevent noise generated when measuring the output power.

However, the magnetic flux density of an Fe-based soft magnetic material such as SEC and SUYP rapidly decreases as the frequency of the applied magnetic field increases. Therefore, when an Fe-based soft magnetic material is used for the motor yoke, the motor torque is significantly reduced when the driving frequency is increased. In addition, when an Fe-based soft magnetic material is used for the core of the electromagnetic flowmeter, when the frequency of the current for generating the magnetic field is increased, the output voltage decreases with a sharp decrease in the magnetic field B, and the measurement of the flow rate itself becomes impossible. It will be difficult.

Further, the magnetic flux density in the high frequency region of a Fe-based soft magnetic material such as SEC and SUYP has a large temperature dependency, and when used in a motor yoke or a core of an electromagnetic flowmeter, the following occurs. Problems also arise.

[0008] When the motor rotates, the temperature of the motor increases due to friction of bearings and the like. The higher the rotation speed, that is, the higher the driving frequency, the higher the frictional heat, and the temperature may rise to about 100 ° C.
Since the motor torque depends on the magnetic flux density of the yoke, fluctuations in the magnetic flux density due to temperature cause variations in the motor torque.

On the other hand, the electromagnetic flow meter is used in a temperature range of -10 ° C. to 160 ° C. However, if the magnetic flux density of the core fluctuates with the temperature, the output voltage also fluctuates, and the measured value of the flow rate varies.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has a magnetic flux density in a high frequency region higher than that of an Fe-based soft magnetic material, and has a small temperature dependency of the magnetic flux density. Cr-based soft magnetic steel is provided.

[0011]

Means for Solving the Problems C: 0.05% by weight%
Hereinafter, Si: 3.0% or less, Mn: 1.0% or less, P:
0.04% or less, S: 0.01% or less, Cr: 5.0%
-18.0%, N: 0.05% or less, Al: 4.0% or less, Ti: 0.5% or less (including no addition), with the balance being Fe and unavoidable impurities. Formula 40 ≦ 4.3 (wt% Cr) +15.1 (wt% Al) +19.1 (wt% Si) +9.
8 is achieved by Fe-Cr soft magnetic steel characterized by satisfying the following conditions:

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have conducted intensive studies to solve the problems, and as a result, by adjusting the amount of each component and the electric resistivity, the magnetic flux density in a high frequency region can be controlled by soft magnetic materials such as SEC and SUYP. It has been found that a material that is higher than the material and has a small temperature dependence of the magnetic flux density can be obtained.

The gist of the present invention will be described below. The present inventors have found that, in Fe—Cr soft magnetic steel, the maximum magnetic flux density Bm at alternating current is greatly affected by the electric resistivity ρ. FIG. 1 shows the relationship between the maximum magnetic flux density Bm and the electrical resistivity at a temperature of 25 ° C. at a plate thickness of 1.0 mmt, a frequency of 500 Hz, and a magnetic field of 10 ersted. Here, the plate thickness is 1.0mmt, frequency 500H
The reason for setting z is that the core material of the motor yoke and the electromagnetic flow meter, which are the main applications of the present invention, often processes a material with a plate thickness of 0.5 mm to 1.0 mmt, the driving frequency of the motor, or the electromagnetic flow meter. The frequency of the current flowing through the exciting coil is 500H
Because it is often z or more. Further, the reason why the magnetic field is set to 10 Elsted is that the magnetic field generated by the exciting coil when there is no core material is often 10 Elsted or more.

FIG. 1 shows that the maximum magnetic flux density Bm is the electric resistivity ρ
It can be seen that it increases sharply with the increase in. This behavior is due to the fact that the higher the electrical resistivity ρ of the material, the smaller the eddy current generated when the material is magnetized by alternating current. That is, since the eddy current generates a magnetic field in a direction opposite to the magnetization, the higher the electrical resistivity ρ of the material, the smaller the eddy current and the larger the magnetic flux density.

On the other hand, FIG. 2 shows a comparison of the temperature dependence of the maximum magnetic flux density Bm of the steel of the present invention, 11Cr-0.6Si steel, and that of the conventional steel, SUYP. The maximum magnetic flux density Bm of SUYP, which is a conventional steel, increases with an increase in temperature, and the difference between Bm at a temperature of 25 ° C and Bm at a temperature of 150 ° C is as large as 1470G. In contrast, the maximum magnetic flux density Bm of the 11Cr-0.6Si steel of the present invention is
Shows the behavior of increasing with temperature as in SUYP, but the increase rate of Bm with respect to temperature is smaller than that of SUYP, and the difference between Bm at 25 ° C and Bm at 150 ° C is as small as 380G.

Such an increase in the maximum magnetic flux density Bm with an increase in temperature is due to the temperature dependence of the electric resistivity ρ. As is generally known, the electrical resistivity ρ increases with an increase in temperature. Therefore, as the temperature increases, the maximum magnetic flux density Bm also increases. However, as can be seen from FIG. 1, the maximum magnetic flux density Bm with respect to the electrical resistivity ρ
Decreases as the electrical resistivity ρ increases. Therefore, the electrical resistivity ρ at a temperature of 25 ° C. is small.
In SUYP, the maximum magnetic flux density B for an increase in the electrical resistivity ρ
The rate of increase of m is large, and the change of the maximum magnetic flux density Bm with respect to temperature is also large. On the other hand, 11Cr-0.6Si
Since the electrical resistivity ρ at a temperature of 25 ° C. is originally large in steel, the rate of increase of the maximum magnetic flux density Bm with respect to the increase of the electrical resistivity ρ is small. Becomes

FIG. 3 shows the effect of electrical resistivity ρ on the difference ΔBm between the maximum magnetic flux density Bm at a temperature of 150 ° C. and the maximum magnetic flux density Bm at a temperature of 25 ° C. ΔBm rapidly decreases with an increase in the electric resistivity ρ. It can be seen that ΔBm is 500 G or less when the electric resistivity ρ is 40 μΩ · cm or more.

The present inventors have also investigated the effects of component elements on the electrical resistivity of Fe—Cr alloys. as a result,
It has been found that the electrical resistivity ρ of the Fe—Cr alloy is expressed by the following equation. ρ = 4.3 (wt% Cr) +15.1 (wt% Al) +19.1 (wt% Si) +9.
8 Therefore, in order to obtain an electric resistivity ρ: 40 μΩ · cm or more, the following equation is used: 40 ≦ 4.3 (wt% Cr) +15.1 (wt% Al) +19.1 (wt% Si) +9.
It turns out that it is sufficient to satisfy 8.

The reasons for limiting the components of the present invention are described below.

C: 0.05% by weight or less C forms a martensite phase harmful to magnetic properties and deteriorates magnetic properties. Therefore, the amount of C was limited to 0.05% by weight or less.

Si: 3.0% by weight or less Si is an element that effectively acts to increase the electric resistivity ρ and increase the maximum magnetic flux density Bm in alternating current. However, it is an element that significantly increases hardness, and excessive addition makes punching difficult and reduces the maximum magnetic flux density Bm. Therefore, the amount of Si is 3.0% by weight.
Limited to the following.

Cr: 5.0 to 18.0% Cr, like Si, has the effect of increasing the electrical resistivity ρ and increasing the maximum magnetic flux density Bm in alternating current, 5.0% by weight.
It is necessary to add above. However, it decreases the maximum magnetic flux density Bm. Therefore, the upper limit was set to 1.0% by weight.

Mn: 1.0% or less Mn is an element inevitably mixed from scrap or the like at the time of steel making.
0% by weight.

P: 0.04% or less P is an element that deteriorates the magnetic properties, so that the content is set to 0.04% by weight or less. S: 0.01% or less S, which is an impurity element, is an element that significantly degrades magnetic properties, and thus needs to be kept low. Therefore, 0.
It was limited to 01% by weight or less.

N: 0.05% or less N, like C, degrades magnetic properties. Therefore,
The amount of N was limited to 0.05% by weight or less.

Al: 4.0% or less Like Si and Cr, Al has the effect of greatly increasing the electrical resistivity ρ and increasing the maximum magnetic flux density Bm in alternating current. However, excessive addition decreases the maximum magnetic flux density Bm.
Therefore, the upper limit of Al was set to 4.0% by weight.

Ti: 0.5% or less (including no addition) Ti forms a carbide more stably than Cr, and thus prevents the formation of a martensite phase harmful to magnetic properties. However, an excessive addition lowers the magnetic flux density, so the upper limit was made 0.5% by weight.

【Example】

The effects of the present invention will be specifically described below with reference to examples.

Table 1 shows the chemical component values (% by weight) of the test steels and
The electric resistivity ρ at 25 ° C. is shown. Of these, A1
A6 steel has a component composition and an electric resistivity ρ specified in the present invention.
, B1 and B2 steels are comparative steels, and B3 steel is SUYP. Each test material was melted in a 30 kg high-frequency melting furnace, and then subjected to forging, hot rolling, cold rolling, finish annealing, and pickling to obtain a steel sheet having a thickness of 1.0 mm.

From each test material, a ring test piece for magnetic measurement having an outer diameter of 45 mm and an inner diameter of 33 mm was cut out and subjected to a temperature of 850 in a vacuum atmosphere.
Magnetic annealing was performed at 0 ° C. for a processing time of 0 min. First, the maximum magnetic flux density Bm of each test piece after the magnetic annealing was measured at a temperature of 25 ° C., a frequency of 500 Hz, and an applied magnetic field of 10 ersted. Then, the material temperature was increased to 150 ° C. by a thermostat, and the maximum magnetic flux density Bm was measured under the same conditions as the temperature of 25 ° C.

Table 2 shows the test results. A which is the steel of the present invention
All 1-A6 steels have a large maximum magnetic flux density Bm at a temperature of 25 ° C. and a temperature of 150 ° C., and the difference ΔBm between the maximum magnetic flux density Bm at a temperature of 150 ° C. and the maximum magnetic flux density Bm at a temperature of 25 ° C.
Is also small. On the other hand, B1 steel, which is a comparative steel, has a small electric resistivity ρ, so that the maximum magnetic flux density Bm is smaller than the inventive steel,
ΔBm is also large. B2 steel has a small ΔBm, but has a large amount of Cr, so that the maximum magnetic flux density Bm is smaller than that of the invention steel. Further, B3 steel (SUYP) has a remarkably low maximum magnetic flux density Bm and ΔBm as large as 1470 G as compared with the invention steel.

[0032]

As described above, according to the present invention, it is possible to obtain Fe-Cr soft magnetic steel having a high maximum magnetic flux density Bm in alternating current and a small temperature dependency of the maximum magnetic flux density Bm.

[Brief description of the drawings]

[Figure 1] Plate thickness 1.0t, frequency 500Hz, applied magnetic field 10 ersted,
It is a figure which shows the relationship between the maximum magnetic flux density Bm at 25 degreeC, and electrical resistivity (rho).

FIG. 2 is a diagram showing a comparison between 11Cr-0.6Si steel of the present invention and SUYP of a conventional steel with respect to the temperature dependence of the maximum magnetic flux density Bm at a plate thickness of 1.0 t, a frequency of 500 Hz, and an applied magnetic field of 10 Oersted. .

FIG. 3 shows a maximum magnetic flux density Bm at a temperature of 150 ° C. and a temperature of 25.
FIG. 3 is a diagram showing the effect of electrical resistivity ρ on the difference ΔBm of the maximum magnetic flux density Bm at ° C.

[Table 1]

[Table 2]

Claims (1)

[Claims] 1. C: 0.05% or less by weight%, Si:
3.0% or less, Mn: 1.0% or less, P: 0.04% or less, S: 0.01% or less, Cr: 5.0% to 18.0
%, N: 0.05% or less, Al: 4.0% or less, Ti:
0.5% or less (including no addition), the balance consisting of Fe and unavoidable impurities, and the following formula: 40 ≦ 4.3 (wt% Cr) + 15.1 (wt% Al) + 19.1 (wt% Si) ) +9.
8 Fe-Cr soft magnetic steel excellent in alternating current magnetic characteristics and temperature characteristics characterized by satisfying (8).