JPS607375A - Method and apparatus for measuring coercive force of ferromagnetic substance test piece - Google Patents

Abstract

PURPOSE:To enable the measurement of a coercive force of a test piece simply at a high accuracy by a method wherein a test piece is magnetized in a solenoid, rotated in front of a head of a detection coil and then, a specified demagnetization is done with a demagnetizing coil. CONSTITUTION:A test piece is magnetized with a magnetizing coil 12 in a solenoid 10 and rotated in front of a head of a detection coil 28 so that the magnetic flux thereof is caused to cross the detection coil 28 at the right angle thereto to generate an induced voltage (e) by an electromagnetic induction. Then, a magnetic field necessary for cancelling the induced voltage (e) is applied anew by a demagnetizing coil 14 from outside to calculate the strength of an external magnetic field necessary for making the induced voltage (e) zero to be used as a coercive force. Thus, the coercive force of the test piece can be measured very simply at a high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring coercive force of a ferromagnetic test piece and an apparatus for carrying out the method.

Iron and other metal materials exhibiting ferromagnetic properties are tested for their magnetic properties as magnetic materials before being shipped from the factory.
It is common practice to sample a test piece of the metal material and measure its magnetization characteristics. This magnetization characteristic is the first
As shown in the figure, when the horizontal axis in a magnetic material is the magnetic field strength 1 and the vertical axis is the magnetic flux density B, the magnetic field strength is 0-
) a → 1] → (It is shown as a magnetization curve that reaches magnetic saturation at the 0 point after changing as shown in 2. When the magnetic field is weakened from the magnetic saturation point C, the strength of magnetization becomes C → d → e → Following the path f, saturating at point f, and then increasing the magnetic field again, the magnetization changes in an annular manner from f to g-+, following the path 1+C, forming a so-called hysteresis loop curve. At this time, the magnitude of Od is called the residual magnetic flux density Br, and the magnitude of Oe is called the coercive force 1-1 c.Measurement of the magnetization characteristics such as magnetic flux density and coercive force of the metal material shipped from the factory is as follows. Conventionally, the ring core method using a ring sample is used, or a self-recording flux meter or NS permeability meter is used. Among these various methods for measuring magnetization characteristics, the retention of bar-shaped test pieces using NS magnetic permeability a1 is particularly important. Magnetic force measurement has the disadvantages of complicated and time-consuming work procedures, and requires skill.

The present invention has been devised in view of the above-mentioned drawbacks inherent in the conventional means for measuring coercive force of a test piece. A magnetic field from a magnetizing coil is applied to a ferromagnetic test piece placed in the solenoid to magnetize the test piece, and the magnetized test piece is rotated relative to a detection coil also placed in the solenoid. An induced voltage is generated in the detection coil, and an external magnetic field necessary to cancel the induced voltage is further applied by a demagnetizing coil to cloud the induced voltage.The strength of the external magnetic field is calculated as the coercive force. Features.

In addition, a coercive force measuring device according to another invention of the present application, which is suitably used to carry out this measuring method, has a solenoid configured by arranging a magnetizing coil and a demagnetizing coil concentrically, and a ferromagnetic force in the solenoid. A test piece holder for attaching a body test piece and a detection coil for detecting induced voltage are arranged facing each other at a predetermined distance apart, and the test piece holder is arranged in line with the detection coil and configured to be rotated relative to the detection coil. This is the first sign.

Next, the coercive force measuring method according to the present invention will be described in detail below in relation to a coercive force measuring apparatus for implementing the method.

Figure 2 shows an outline of the coercive force measuring device according to the present invention.
6 components, and reference numeral 10 indicates a solenoid of a predetermined diameter, that is, a cylindrical air core. The solenoid 10 includes a magnetizing coil 12 formed by winding a fi/U wire a predetermined number of times around a bobbin (not shown), and a magnetizing coil 12 which is also wound around a bobbin (not shown) and closely concentrically arranged inside the magnetizing coil 12. It basically consists of a magnetic coil 14 and the like.

Further, a cylindrical metal magnetic shield plate 16 is disposed in close contact with the outer circumferential portion of the solenoid 10 .

The solenoid 10 is a housing (not shown) of the measuring device.
The magnetizing coil 12 and demagnetizing coil 14 included in the solenoid are housed within the solenoid, and power supply lines 18 and 20 are led out from the magnetizing coil 12 and demagnetizing coil 14, respectively, and are connected to dedicated DC power supplies 22 and 24, respectively.

Further, in the cavity of the solenoid 10, a test piece holder 26 and a detection coil 28 are arranged facing each other at a predetermined distance apart, with their respective axes aligned with the central axis of the solenoid. (described below in connection with the figure). The test piece holder 2G is fixed to one end of a rotating shaft 30 extending outward in the axial direction of the solenoid 10, as shown in FIG. It is rotatably supported horizontally by a pair of bearings 34 provided on a supporting stand 32. In addition, the rotating shaft 3
The other end of the DC motor 36 is connected to the rotation shaft of a DC motor 36 whose rotation speed can be adjusted steplessly.

The detection coil 28 is attached to one end of a metal hollow pipe 38, and the hollow vibe 38 is also aligned with the central axis of the solenoid 10 and extends horizontally, like the rotating shaft 30. The other end of the hollow vibrator 38 is fixed to the housing by appropriate means outside the solenoid I<IO. Note that the detection coil 2
A wire 40 is connected to the hollow pipe 38 and connected to an appropriate measuring circuit. This measurement circuit includes, for example, a detection amplifier 112 .
Capacitor 44. The X-Y recorder 48 is constructed in a block-like manner from an AC voltage H146 and an X-Y recorder 48.
The X terminal of the demagnetizing coil 14 is connected to a standard resistor 50 inserted in the power supply line 2o connecting the demagnetizing coil 14 and its DC power source 24 with an intermediate tap.

Next, an enlarged view of the circular part indicated by the symbol in Fig. 2,
It is shown in Figure 3. That is, FIG. 3 shows the test piece holder 2.
6 and the detection coil 28, the boulder 26 is composed of a circular member and is screwed into the end of the rotating shaft 3o to be fixed thereto. . A ferromagnetic test piece 52 made of a metal material such as iron is eccentrically bored into the end face of the bolt 26 at a predetermined depth.
It can be inserted into a storage hole with an opening, and can be detachably attached using an appropriate fixing means. The test piece 52 is magnetized by an external magnetic field as will be described later, and the test piece 52 is attached in such a position that the direction of magnetic flux generation is parallel to the central axis of the holder 26.

The detection coil 28, which is disposed facing the test piece 2G with a predetermined gap in front of it in the axial direction, is made by winding a copper wire around two acrylic bobbins 54a and 54b, for example, as shown in FIG. The two bobbins are rotated, and the centers of the two bobbins are slightly offset from the axis of the hollow pipe 38, respectively. Note that the copper wires of the two bobbins are connected to the magnetization coil 12.
In order to cancel the applied magnetic field generated when the bobbins 54a and 54b are excited, the bobbins 54a and 54b are wound in opposite directions. Further, the most appropriate distance between the detection head of the detection coil 28 and the test piece 52 attached to the holder 26 is determined experimentally, but generally it is 1.0mar-2.0no.
It is preferable to set it to n.

A coil indicated by reference numeral 56 in FIGS. 2 and 3 is provided as an option for heating the test piece 52 and measuring the development of magnetization characteristics over time as the temperature of the test piece increases. be.

That is, a bobbin 58 made of magnetically permeable heat-resistant porcelain is attached to the end of the hollow pipe 38 through a support member (not shown).
is attached to the bobbin 58, and a coil 56 made of a wire with high electrical resistance such as nichrome wire is wound around the outer circumference of the bobbin 58 so as to heat the test piece 52 located inside the holter 26 to a predetermined temperature. It has become. In the case where this heating coil 56 is provided, the material of the bobbin 548.degree. 54b of the detection coil 28 must be replaced with the acrylic resin and replaced with a heat-resistant material such as non-magnetic copper. In addition, in order to minimize the thermal influence on the detection coil 28, as shown in FIG. That's af.

In the embodiment shown in FIGS. 2 and 3, the test piece holder 26 is driven by the motor 36 to rotate, and the detection coil 28 is stationary at a fixed position. 28 may be rotated, and the test piece holder 26 may be kept stationary. Therefore, the rotational relationship between the test piece holder 26 and the detection coil 28 is relative to each other.

Next, a method for measuring the coercive force of a ferromagnetic test piece using the coercive force measuring apparatus according to the present invention configured as described above will be explained. Prior to the start of measurement, a bar-shaped test piece 52 of predetermined dimensions (for example, diameter 5 mm, maximum length 30 nm) is obtained from a metal material made of iron or other ferromagnetic material, and this test piece 52 is placed in the holder 26 having the above-described configuration. Take it to 4.

During this installation work, the test piece holder 2G is moved back in the axial direction together with the support base 32 by a slide mechanism (not shown) to position the holder 26 outside the solenoid 10, and in this state, the test piece 52 is installed. It has become so. Next, the test piece holder 26 is slid and inserted into the solenoid 10, and the position is set so that a predetermined gap is obtained between the detection coil 28 and the test piece 52.

After completing the test piece 52 in this manner.

The magnetization coil 12 is excited by the DC power supply 22 to apply a magnetic field to the internal space of the solenoid 10. (For example, the current of the DC power supply for jy is 15Δ, and the maximum applied magnetic field is 8
It is 600e. Strong (i, +,) in this opening force 11 magnetic field
By placing a test piece 52 made of a magnetic substance, the test piece is magnetized at tJ and 0°C as shown in the graph of FIG.
Magnetic saturation is reached at the point. After reaching the magnetic saturation point C, when the magnetic field formed by the magnetizing coil 12 is weakened, the strength of magnetization decreases and reaches 4 points of residual magnetization when the magnetic field is zero. saturate. At this point, the excitation of the magnetizing coil 12 is stopped by (.1).

Next, the motor 3G shown in FIG. ,+
: Examine the shaft 30 and its tip (J test piece holder, 2
G is rotated (the number of rotations is, for example, 100 to 7 (,1
(selected in the +rpm range). The test piece 52, which has already been magnetized due to stiffness, is also
The magnetic flux 60 generated from the test piece 52 rotates in front of the detection coil 28 disposed at l+, and as shown in FIG. 5, the magnetic flux 60 generated from the test piece 52 passes through the detection coil 28 periodically. That is, as a result of eccentrically rotating the test piece 52 in front of the detection coil 28, the magnetic flux passing through the detection coil is changed, and an induced voltage e is generated in the detection coil based on the principle of electromagnetic induction.

Further, substantially in synchronization with the start of rotation of the test piece holder 26, the demagnetizing coil 14 is excited by the DC power supply 24 (for example, current IA), and a new external magnetic field is applied to the solenoid 10. The magnetic field applied by this demagnetizing coil 14 is opposite to the direction of the magnetic field applied by the magnetizing coil 12,
The strength is, for example, the maximum applied magnetic field of 200e,
The amount is sufficient to cancel the magnetization of the test piece induced in the detection coil 28. Due to this, the residual magnetization of the test piece is reduced, and the induced voltage is also reduced accordingly. The relationship between the current flowing through this demagnetizing coil 14 and the induced voltage is expressed as X-
(2) Instruct with the recorder 48, calculate the magnetic field from the value at which the induced voltage e becomes zero by an appropriate calculation answer, and use the strength of this external magnetic field as the coercive force.

When measuring the coercive force using the heating coil 56 provided as an option, the coil 5G raises the test piece 52 to a predetermined temperature, and the temperature changes over time as the temperature changes. Changes in magnetization 'l'l' properties can be easily measured.

As described above, according to the method and apparatus for determining the magnetic coercivity of a test piece according to the present invention, the test piece is magnetized in the solenoid 1 by a magnetizing coil,
ffh J 'l is rotated in front of the head of the detection coil, and its magnetic flux crosses the detection coil in the perpendicular direction at 21 L, causing an electromotive force Qq of 44 on the principle of electromagnetic induction. Then, the magnetic field necessary to cancel this induced voltage C is newly applied externally using a demagnetizing coil.
i'+ii not mentioned γ required to make the induced voltage e zero!
The coercive force is calculated using the strength of li fiR"11'.

Therefore, according to the present invention, it is possible to easily and accurately measure the coercive horn of a test piece in an extremely simple sanding procedure.
I do it. In this way, conventionally it took 1-2 hours to measure the coercive force, but according to the present invention, such difficulties can be completely overcome and This method has many beneficial effects, such as making it possible to measure the coercive force of test pieces not only in the shape of 4 or 4 years old, but also in annular shapes.

[Brief explanation of the drawing]

FIG. 1 is a magnetic 1-hi curve diagram showing the relationship between magnetic field strength I4 and magnetic flux density B in a magnetic material, FIG. The figure is an enlarged view of the circular part indicated by the symbol A in Fig. 2, Fig. 4 is a perspective view of one embodiment of the detection coil, and Fig. 5 is a test piece rotated in 4 and 2 directions with respect to the detection coil. FIG. 3 is an explanatory diagram showing changes in magnetic flux when 10... Solenoid 12... Magnetizing coil 14
... Demagnetizing coil 2G ... Test piece holder 28.
...Detection coil patent applicant Daido Steel Co., Ltd.

Claims (2)

[Claims] (1) Apply a magnetic field from a magnetizing coil to a ferromagnetic test piece placed in the solenoid to magnetize the test piece, and make the magnetized test piece relative to the detection coil also placed in the solenoid. to generate an induced voltage in the detection coil, and further apply an external magnetic field necessary to cancel the induced voltage by a demagnetizing coil, and the strength of the external magnetic field to make the induced voltage zero is used as the coercive force. A method for measuring coercive force of a ferromagnetic test piece, characterized by calculating the coercive force of a ferromagnetic test piece. (2) A solenoid is constructed by arranging a magnetizing coil and a demagnetizing coil concentrically, and a test piece holder for mounting a ferromagnetic test piece in the solenoid and a detection coil for detecting induced voltage are arranged in a predetermined layer. An apparatus for measuring coercive force of a ferromagnetic test piece, characterized in that RIGs 11 are arranged opposite to each other and the test piece holder can be rotated relative to a detection coil.