JPS62294987A - Method and apparatus for measuring magnetic property - Google Patents

Abstract

PURPOSE:To enable online measurement, by a method wherein a DC current energizing an electromagnet is adjusted based on a transfer rate to DC magnetize metal material at a fixed magnetic flux density so that the detecting position of a ceramic detector follows a specified part thereof. CONSTITUTION:Electromagnets 103 and 104 are provided below a steel plate separated from each other at a proper distance in a transfer direction and currents is fed from a DC power source 105 to reverse the direction of magnetic fields which the electromagnets 103 and 104 apply to the steel plate respectively. The DC power source 105 can control the magnetizing force constantly by adjusting the values of the currents outputted from the electromagnets 103 and 104 based on a speed signal from a speed detector 4. In this case, the magnetic fields 103a and 104a are opposite in the direction respectively between the position (E) with the electromagnet 103 and the position (F) with the electromagnet 104 and the intensity of the magnetic fields also opposite in the polarity. Thus, hysteresis loop can be measured for all quadrants on a coordinate thereby enabling online measurement of various magnetic properties such as magnetic permeability, differential magnetic permeability at a high accuracy. The measurement of a cold processing level or the like is also possible.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method and apparatus for measuring the magnetic properties of a metal material, and more specifically, to a method and an apparatus for measuring the magnetic properties of the above-mentioned metal material. The present invention relates to a method and apparatus for continuously and accurately measuring in a line.

[Prior art]

There are measurement methods that utilize the magnetic properties of steel to measure the mechanical properties, grain size, etc. of steel. To explain the case of measuring the grain size of steel materials, for example, there is a method disclosed in Japanese Patent Publication No. 52-40528.

This method uses a detection coil to detect changes in the magnetic flux density of the steel material during the process of saturation magnetizing the steel material, which is the material to be measured, using an electromagnet.The output signal, that is, the signal representing the magnetization curve, is amplified, and the pulse intensity is The magnetization levels of each class are classified using multiple sampling circuits, and the height of the magnetization level of each class is detected using a pulse wave height analyzer to determine the magnetization level distribution (see Figure 8), and its shape or characteristic shape is determined. This method calculates the grain size based on the total number of pulses in portions C and D.

The pulse is magnetic noise and is called Barkhausen noise. It has long been known that the total number of pulses has a correlation with the grain size, and this correlation shows that when a steel material is saturated magnetized using a current with a low frequency, for example, a frequency of about 0.01 to 0.1 tlz, the magnetization It is determined by measuring the total number of pulses generated by the steel material per unit period.

It is also known that the mechanical properties of steel, such as hardness, tensile strength, and width, are influenced by carbon content. Figure 9 is a graph showing the relationship between carbon content on the horizontal axis and residual magnetic flux density Br and coercive force +1c on the vertical axis under various heat treatment conditions. There is an approximate relationship between coercive force and carbon content. Therefore, in the example shown in this figure, if the heat treatment conditions are the same, the carbon content, that is, the mechanical properties, can be estimated by DC magnetizing the steel material and measuring its residual magnetic flux density and/or zero magnetic force.

Furthermore, it is known that the mechanical properties of steel materials are also influenced by the degree of cold working. In Figure 1θ, the horizontal axis shows the cold working rate (
%) and the relative magnetic permeability -1 on the vertical axis, this is a graph showing the relationship between the two in various cases of different types of stainless steel materials. There is a relationship. Therefore, by magnetizing the steel material with direct current and measuring its magnetic permeability, the degree of cold work, that is, the mechanical properties can be estimated.

In this way, the mechanical properties of steel, the grain size, the magnetic properties,
That is, it can be measured by using the above-mentioned Barkhausen noise, residual magnetic flux density, coercive force, magnetic permeability, etc.

[Problem that the invention seeks to solve]

However, when measuring the magnetic properties of steel materials online, as shown in Figure 11, when the transport speed of the steel material (horizontal axis) changes, the magnetic flux density received per unit volume of the steel material (vertical axis) changes, and ) When performing measurements, there was a problem in that accurate measurements could not be performed because the measurement position moved over the steel material during the measurement and spread over a wide range.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method and apparatus for measuring magnetic properties that can accurately measure on-line the magnetic properties of metal materials being transported through a production line or the like.

[Means for solving problems]

The present invention changes the strength of the magnetic field according to the transport speed of the metal material, magnetizes the metal material with a constant magnetic flux density with direct current, and provides magnetic detection that faces the magnetized metal material part along the transport direction. Among the signals detected by the instrument, the magnetic characteristics are measured using signals from the same part of the metal. That is, the method for measuring magnetic properties according to the present invention detects the transfer speed of the metal material to be transferred, and magnetizes the metal material (by adjusting the Vi current flowing to the provided electromagnet based on the transfer speed). The material is DC-magnetized with a constant magnetic flux density, and the detection position of a magnetic detector provided facing the DC-magnetized part of the metal material is made to follow a specific part of the metal material.

〔Example〕

The present invention will be specifically explained below based on the drawings.

FIG. 1 is a schematic diagram showing an implementation state when the present invention is applied to measurement of residual magnetic flux density, and 1 in the figure indicates a steel plate. The steel plate 1 is being transferred in the direction of the outlined arrow, and a speed detector 4 and a yoke-shaped electromagnet 3 are provided below the steel plate 1 to detect the transfer speed. The electromagnet 3 has its axis aligned with the transfer direction, and the excitation coil 3a is attached to the body 2 of the U-shaped iron core 2.
Both ends of the iron core 2 of the electromagnet 3 are bent toward the steel plate 1 to form magnetic poles 2b and 2c.

The excitation coil 3a is connected to DC type #5,
A transfer speed signal detected from the speed detector 4 is input to the DC power source 5. The DC power supply 5 adjusts the output current to be large when the transfer speed is fast, and to reduce the output current when the transfer speed is slow, and supplies this to the excitation coil 3a, which magnetizes the steel plate 1 with DC current.

A plurality of magnetic detectors 11 are placed on the opposite side of the electromagnet 3 across the steel plate 1. . . , 1n, for example, detection coils are provided at appropriate distances from each other along the transport direction.

The detected signals are applied to the filter 7, where only signals in the required frequency band are extracted and input to the arithmetic unit 40.

The transfer speed signal detected by the speed detector 4 is input to the calculation unit 40, and the calculation unit 40 reads the signals at the same location on the steel plate 1 based on this input signal. Magnetic detector 11. . . , filters 21 to which signals are input from In. . . , 21 is determined, and the residual magnetic flux density is measured by detecting a hysteresis loop based on the signal read at that timing.

A method for measuring residual magnetic flux density using the magnetic temporal measurement device of the present invention configured as described above will be explained.

When the transfer speed of the steel plate l is detected by the speed detector-4,
Based on the detection signal, the DC power supply 5 adjusts the output current so as to keep the steel magnetic flux density, which changes in response to changes in the steel material transfer speed, to a constant value, as shown in FIG. 11.

In Figure 2, for example, nine magnetic detectors are installed, and the detection positions on the steel plate are shown in a and b from the downstream side.

Let c, d, e, f, g, h, and i, and let e be the position on the steel plate facing the middle position of magnetic poles 2b and 2c of electromagnet 3, and furthermore, let the maximum magnetic field strength by the electromagnet at position e be of)
This is a graph showing the equal magnetic field distribution by the electromagnet 3 based on the strength of the magnetic field at each position when Ieff is set, and by adjusting the output current by the DC power supply 5, Ieff is controlled to an appropriate level according to the transfer speed. Ru. As a result, the magnetic flux density reaching the steel plate 1 gradually increases while being transported through the magnetic field with the mountain-shaped distribution, and after reaching the maximum value, it gradually decreases, but by controlling the DC power supply, The maximum value is a constant value regardless of the transfer speed. For this reason, the steel plate 1 is magnetized with a constant amount of direct current.

Figure 3 is a graph showing the relationship between the magnetic field strength 11 on the horizontal axis and the magnetic flux density B on the line as the steel plate 1 is magnetized and demagnetized by the electromagnet 3 for one point on the steel plate 1. It is. a, b, c...i in the figure are the same as those in FIG. 2, and a', b' to 50...1' is the position a,
The values of the magnetic flux density B of the steel plate 1 subjected to each magnetic field strength I4 at b, c, . . . i are shown.

As can be understood from this figure, one measurement point on HRFj,I is +4 and B while being transferred through the range covered by the magnetic field from electromagnet 3.
The relationship between the two is the point on the hysteresis loop A in the first quadrant.

On the other hand, the calculation unit 40 determines whether one measurement point of the steel plate 1 is at each position a or b based on the J speed signal transferred from the speed detector 4.

Filters 21 . ..., reads the signal that has passed through 2n at the determined timing. Therefore, it is possible to detect magnetic changes in the same cylindrical location of the steel plate 1 over time.

The calculation unit 40 contains in advance the strength F of the magnetic field from the electromagnet 3 at positions a, b, c, . When the calculation unit 40 reads the magnetic flux density number, it calculates the hysteresis loop A for the 1 iJ'J fixed point of the steel plate 1 from the relationship between the magnetic field strength H and the magnetic flux density B, and calculates the magnetic field after excitation. The residual magnetic flux density Br when the strength I (becomes zero)
(see FIG. 3), hardness, tensile strength, etc. are measured based on the residual magnetic flux density and the above relational expression, and these are displayed on a display (not shown).

By providing a multi-channel analyzer in place of the /i1'W section 40, the number of Barkhausen noises emitted from the steel plate l when the magnetization strength is changed can be measured. By using the grain size measurement method of No.-1 (No. 1) or by using a calibration curve, highly accurate on-line measurement of grain size can be achieved.

FIG. 4 is a schematic diagram showing another embodiment of the present invention.
The same parts as those in the figure are given the same numbers.

Electromagnets 103 and 104 are provided below the steel plate 1 at an appropriate distance apart in the transfer direction, and are connected to a DC power source 105 so that the directions of the magnetic fields exerted by the electromagnets 103 and 104 on the steel plate 1 are opposite to each other. Is the current flowing in each case? It's starting to look like this. The DC power supply 105 can control the magnetizing force to a constant level by adjusting the current value output to the electromagnets 103 and 104 based on the speed signal from the speed detector 4.

In the case of the apparatus of the present invention configured in this way, as shown in FIG.
In case (F) according to 04, the respective magnetic fields 103a and 104
a is in the opposite direction, and the strength of the magnetic field is positive and negative. Therefore, as shown in FIG. 6, the first . 2.
3. It is possible to measure hysteresis loops in four phenomena, which not only determine the residual magnetic flux density but also various magnetic properties, e.g. permeability.

Differential magnetic permeability, etc. can be measured online with high accuracy, and cold working degree, etc. can also be measured.

Although a yoke type electromagnet is used in the above two embodiments, the present invention is not limited to this, and can be similarly implemented using a point ball type electromagnet as shown in FIG. 7 in comparison with FIG. 1.

Further, in the above description, the magnetic detectors are arranged at regular intervals, but the present invention is not limited to this, and the present invention may also be implemented by using a magnetic detector in which a plurality of detection coils or magnetically sensitive elements are arranged continuously without any gaps. Of course, the present invention can also be implemented by moving one detection coil or magnetically sensitive element at the same speed as the steel plate 1. In this case, continuous or more clearly defined hysteresis loops can be measured.

Further, in the above embodiment, the magnetic properties of a steel plate are measured, but the present invention is not limited to this, and it goes without saying that the magnetic properties of paramagnetic and diferromagnetic metal materials in general can be measured.

〔effect〕

As described in detail above, according to the present invention, the transport is carried out.

It is possible to direct current magnetize the metal material being transported at a constant magnetic flux density regardless of the transfer speed, and it is also possible to perform spot measurements of magnetic properties at one measurement point. It is now possible to measure online and also the mechanical properties of metal materials.

The present invention has excellent effects such as being able to measure crystal grain size and the like.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the implementation state of the present invention, Fig. 2 is a distribution diagram of the strength of the magnetic field emitted from the electromagnet, Fig. 3 is a graph showing the relationship between the strength of the magnetic field and magnetic flux density, and Fig. 4 is a graph showing the relationship between the strength of the magnetic field and the magnetic flux density. Another embodiment of the present invention, FIG. 5 is an explanatory diagram of the measuring method in that case, FIG. 6 is an explanatory diagram of the measurable range in that case, FIG. 7 is another embodiment of the present invention, and FIG. An explanatory diagram of the conventional method for measuring grain size, Figure 9 is a diagram of the relationship between residual magnetic flux density, coercive force, and carbon content, Figure 10 is a diagram of the relationship between degree of cold work and magnetic permeability, and Figure 11 is a diagram of the relationship between the degree of cold work and magnetic permeability. It is a relation diagram between steel material transfer speed and steel material magnetic flux density. 1... Steel plate 3, 103.104.203... Electromagnet 4... Speed detector 5,105... DC type J, Tsur 11. ..., in...Magnetic detector 40...Computation unit patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono d Fig. 2 Fig. 3 Fig. 5 Fig. 8

Claims (1)

[Claims] 1. Detecting the transfer speed of the metal material to be transferred, and adjusting the DC current applied to an electromagnet provided to magnetize the metal material based on the transfer speed, so that the metal material is kept at a constant magnetic flux density. A method for measuring magnetic properties characterized by direct current magnetization and causing the detection position of a magnetic detector placed facing the direct current magnetized portion to follow a specific portion of the metal material. 2. A speed detector that detects the transfer speed of the metal material to be transferred; an electromagnet that magnetizes the metal material with DC current; a DC power source that adjusts the current flowing to the electromagnet based on the current flow, and a magnetic detector that is placed facing the metal material that is to be magnetized with direct current and that can detect magnetic characteristics at multiple positions in the transport direction of the metal material. A device for measuring magnetic properties, comprising: a device for scanning a detection position of a magnetic detector based on the detected transfer speed.