JP3546298B2 - Dissimilar material determination method and apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for judging a different material from a test material made of a metal material sequentially conveyed on a conveying line, for example.
[0002]
[Prior art]
For example, in a factory where steel pipes, round bars and other bar materials are manufactured, there are cases where bar materials of different materials having the same or similar shape are mixed and conveyed on the same conveyance line. For this reason, in such a transport line, a different material determination inspection is performed on a strip steel material or the like that is sequentially transported.
[0003]
Conventionally, as this kind of different material determination method, for example, a method of determining by a spark test, a method of determining by analyzing emission spectrum, a method of determining by measuring physical property values such as impedance, coercive force, magnetic permeability, and the like are known. Have been.
[0004]
[Problems to be solved by the invention]
However, in the determination method based on the spark test, since it is a sensory test by a human, there is a problem that erroneous determination is likely to occur, and there is a problem that the test takes time. In addition, in the determination method based on emission spectroscopy, there is a problem that the cost is increased due to the use of the emission spectroscopy analyzer, and there is a problem that the analysis takes time. Since the surface needs to be finished smoothly, there is also a problem that it takes time and effort.
[0005]
Further, among the determination methods based on physical property values, in a method using eddy current flaw detection as disclosed in, for example, JP-A-57-69246 and JP-A-57-128842, the impedance of the test material is measured. There is a problem that the accuracy of the determination is reduced due to the influence of the resistance value, the conductivity, the magnetic permeability, and the like. The method of measuring the coercive force and the magnetic permeability has a problem that a long time is required for the measurement and the measurement efficiency is poor. Further, in the conventional method using the eddy current flaw detection, since reference materials corresponding to the material, shape, dimensions, etc. are used, it is necessary to prepare various kinds of reference materials in advance and replace them according to the test material. In some cases, it is necessary to perform calibration in consideration of the effects of the component composition and the manufacturing history.
[0006]
The present invention has been made in view of such conventional problems, and a first object of the present invention is to eliminate the need for a reference material, to provide a component of a test material, a production history (a crystal grain size, a decarburized layer, and the like). An object of the present invention is to provide a different material determination method that can easily and reliably determine a different material without being affected by a different material.
Further, a second object of the present invention is to provide a dissimilar material judging device which can execute the above dissimilar material judging method simply and inexpensively.
[0007]
[Means for Solving the Problems]
The invention according to claim 1, which achieves the first object, is characterized in that, prior to the determination of a different material of a test material lot composed of magnetic materials having the same components and the same rolling chance, at least one test material in the initial stage of the lot, The background noise level of the leakage magnetic flux is measured in the longitudinal direction of the test material, and a normal value range of at least two noise characteristics of a maximum value, a minimum value, and a maximum value-minimum value is set from the measured noise level. ,
Thereafter, a maximum value, a minimum value, and a minimum value obtained from the noise level measured in the longitudinal direction for the other test materials, based on a comparison between at least two noise characteristics of the noise characteristics and the normal value range. It is characterized by determining a different material.
[0008]
According to the first aspect of the present invention, the noise level of the leakage magnetic flux of at least one test material in the initial stage is measured for each lot and the normal value range of the noise characteristic is set, so that it is not necessary to use the reference material. In addition, since there is little variation in component composition and manufacturing history within a lot, there is no need to consider the effects of these. The leakage magnetic flux noise level is affected only by the magnetic permeability and is not affected by the resistance value or the conductivity, so that the discrimination accuracy is improved. As described above, in the same lot having the same component composition and manufacturing history, the magnetic permeability is substantially constant and the noise level is also substantially the same, so that no reference material is required, and no special calibration is required. Accurate different material discrimination becomes possible.
In addition, the noise level of the leakage magnetic flux can be measured using a normal leakage magnetic flux flaw detector, and the measurement surface can be finished only by passing through a shot blast or leveler. it can.
[0009]
Further, the invention of a dissimilar material determination device according to claim 2 which achieves the second object is a leakage magnetic flux detecting means for detecting a leakage magnetic flux and converting it into an electric signal,
From the output of the electrical signal, a band filter that cuts off the output due to the defect of the test material,
A noise characteristic measuring means for storing a maximum value and a minimum value of the noise level from the electric signal output after the cutoff and calculating a maximum value-minimum value from the maximum value and the minimum value to obtain each noise characteristic; ,
A normal value range setting means for setting a normal value range from any two or more noise characteristics of the obtained maximum value, minimum value, and maximum value-minimum value;
Determining means for determining a different material based on a comparison between the normal value range and two or more noise characteristics by the noise characteristic measuring means,
The normal value range setting means sets the normal value range based on the noise characteristics measured by the noise characteristic measuring means of at least one test material at the beginning of the test material lot having the same component and the same rolling chance. Control means for controlling the inspection material to determine a different material based on a comparison between the noise characteristic measured by the noise characteristic measurement means and the normal value range of the test material in the determination means. It is assumed that.
[0010]
According to the second aspect of the present invention, since a flaw detection device based on ordinary leakage magnetic flux measurement can be used, it can be implemented simply and inexpensively.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing one embodiment of a dissimilar material judging device for performing the dissimilar material judging method according to the present invention. In the present embodiment, a leakage magnetic flux detection unit 3 provided with an electromagnet and a magneto-electric conversion element is installed on the transport line 1 so that the test material 2 sequentially transported on the transport line 1 passes. The leakage magnetic flux detecting section 3 is connected to the noise characteristic measuring section 4 to continuously or intermittently measure the background noise characteristic of the leakage magnetic flux for a predetermined length in the transport direction of each test material 2 and to measure the background noise characteristic. The noise characteristics are supplied to the determination unit 5. The determination unit 5 determines a different material based on the noise characteristic from the noise characteristic measurement unit 4 under the control of the control device 6, and supplies the determination result to the control device 6. In the control device 6, on the basis of the result of the determination by the determination unit 5, for example, a marking device (not shown) is driven to apply marking to the different material, or a sorting device (not shown) is driven to send a regular steel material and a different material from the transport line 1. And sort them out.
[0012]
FIG. 2 is a block diagram showing a detailed configuration of the dissimilar material determination device shown in FIG. The leakage magnetic flux detection unit 3 can use a commonly used leakage magnetic flux flaw detection device as it is, and as shown in FIG. 3, is configured to include a pair of electromagnets 31 and magnetoelectric conversion elements 32 on a gantry 33. The magnetic field lines are passed through the surface of the test material 2 by the electromagnet 31, and the magnetic field lines (leakage magnetic flux) leaking from the surface of the test material 2 are detected by the magnetoelectric conversion element 32 and converted into electric signals. If necessary, the output of the electric signal can be confirmed by the waveform using a display device or a printing device (not shown). The output obtained by converting the detected leakage magnetic flux by the magneto-electric conversion element 32 is sent to the noise measuring unit 4.
The noise measuring unit 4 includes a band filter 41, a maximum value peak memory 42, a minimum value peak memory 43, and a differentiator 44. In the noise measuring section 4, first, the band filter 41 cuts off the output waveform caused by the defect of the test material from the output waveform to obtain a waveform including only noise. The maximum value and the minimum value are obtained from the noise-only electric signal within the certain section thus obtained, and stored in the maximum value peak memory 42 and the minimum value peak memory 43, respectively. The maximum value-the minimum value is calculated.
[0013]
The determination unit 5 includes a switch circuit 51, a normal value range setting circuit 52, and a determination circuit 53. The noise characteristics (the maximum value and the minimum value obtained from the background noise) transmitted from the noise measurement unit 4 are included. And any one of the maximum value and the minimum value) is received by an electric signal, and selectively transmitted to the normal value range setting circuit 52 and the determination circuit 53 via the switch circuit 51 under the control of the control device 6. Supply. The normal value range setting circuit 52 sets a normal value range of any one of the two noise characteristics according to a necessary determination level.
[0014]
The normal value range set by the normal value range setting circuit 52 is supplied to the determination circuit 53, and is compared with any two noise characteristics obtained from the noise signal supplied through the switch circuit 51. If it is within the value range, it is determined to be a normal steel bar, and if it is out of the normal value range, it is determined to be a different material, and the determination result is supplied to the control device 6.
[0015]
Next, the operation of the present embodiment will be described.
First, prior to the determination of a different material of a test material lot having the same component and the same rolling chance, the control device 6 switches the switch circuit 51 so that the output of the noise measuring unit 4 is supplied to the normal value range setting circuit 52. In this state, the background noise is measured for a predetermined length in the length direction (transport direction) of one or more test materials 2 at the beginning of the lot conveyed on the transport line 1. Then, the noise characteristics obtained by the maximum value peak memory 42, the minimum value peak memory 43, and the differentiator 44 are supplied to the normal value range setting circuit 52 via the switch circuit 51, and the normal value range is set. The accuracy is increased by increasing the measurement length (section) of the background noise, but it is desirable to measure so as to include at least one rotation of the probe or the straight rod.
Prior to obtaining the noise characteristic, it is necessary to remove the waveform caused by the defect by the band filter 41 of the measuring unit 4 in order to make a waveform of only the background noise in advance. For example, a serious defect such as a barb or a crack is detected as having an S / N of 2 or more. In this case, the threshold value is set so that the band filter 41 cuts off S / N ≧ 2. Just fine.
[0016]
In order to set a normal value range from a signal of only background noise, first, when one test material 2 at the beginning of a lot is used for setting, the test material 2 is obtained continuously or intermittently. From the noise in the predetermined section, at least two noise characteristics of the maximum value, the minimum value, and the maximum value-minimum value are obtained by the maximum value peak memory 42, the minimum value peak memory, and the differentiator 44. When a plurality of test materials 2 are used, for example, noise characteristics of the plurality of test materials 2 are obtained in the same manner, and an average value thereof is used.
Here, the above noise characteristics are shown in FIG. FIG. 4 is an enlarged view of the waveform of only the background noise excluding the waveform due to the defect. In FIG. 4, a is the maximum value and b is the minimum value. Then, the maximum value-the minimum value, that is, ab is obtained by the operation of the difference unit 44.
[0017]
Based on the thus obtained a (maximum value), b (minimum value) and ab, a normal value range (criterion) is set according to the discrimination level. This will be described with a specific example.
FIG. 5 shows the waveform of the background noise measured for the test materials of JIS 45C and SUJ2. When seeking the target Kenzai noise characteristics from these waveforms, at _{S45C, a 1 = 10.0%,} b 1 = 7.5%, a 1 -b 1 = 2.5%, with _{SUJ2, a 2 = 16.3%,} b 2 = 12.5 %, A ₂ −b ₂ = 3.8%. In order to detect one of them as a dissimilar material from a test material in which two types of steels are mixed, a judgment value A, B, and C are provided, and if any one of the following expressions is satisfied, the dissimilar material is determined. judge. Note that the determination values A, B, and C are determined according to noise measurement accuracy and a required determination level.
| A ₁ −a ₂ | ≧ A (1)
│b ₁ −b ₂ │ ≧ B (2)
| (A ₁ −b ₁ ) − (a ₂ −b ₂ ) | ≧ C (3)
In the case of the 2 _{grades, a 1 -a 2 = 6.3%} , b 1 -b 2 = 5.0%, (a 1 -b 1) - Since the _{(a 2 -b 2) = 1.3} %, for example A = 3.0%, B = 3.0%, and C = 1.0%, the two can be distinguished from each other, and the different materials can be distinguished. That is, in this example, when S45C is a regular material, the normal value ranges of the noise characteristics of a, b, and ab are a ≦ 10.0 + 3.0 = 13.0, b ≦ 7.5 + 3. 0 = 10.5, a−b ≦ 2.5 + 1.0 = 3.5.
The above setting operation of the normal value range is performed for each lot of the test material under the control of the control device 6.
[0018]
When the setting of the normal value range is completed, the normal value range is supplied to the determination circuit 53, and the control device 6 controls the switch circuit 51 so that the output of the noise characteristic measured by the noise measuring unit 4 is supplied to the determination circuit 53. Switch. In this state, the noise characteristic of the test material 2 that subsequently passes through the leakage magnetic flux detection unit 3 is measured by the noise measurement unit 4 and supplied to the determination circuit 53 via the switch circuit 51, where it is compared with the normal value range. Then, it is determined whether the test material 2 is a legitimate steel bar or a different material.
[0019]
As described above, according to the present embodiment, if the noise characteristics of the test materials 2 are the same in the lot, the background noise of the leakage magnetic flux is the difference between the components and the difference in the surface decarburized layer due to the difference in the heating conditions. Focusing on the fact that it is not affected by the difference in the crystal grain size due to the difference in the rolling temperature or the precipitate but only by the magnetic permeability of the test material 2, The noise characteristic of the test material 2 is measured, a normal value range is set from the measured noise characteristic, and the test material 2 thereafter uses the reference material based on the comparison with the measured noise characteristic normal value range. Since the dissimilar material is determined without any need, an operation such as calibration is not required, and the dissimilar material can be always easily and reliably determined.
Further, a known flaw detection device can be used for detecting the leakage magnetic flux, so that it can be simple and inexpensive.
[0020]
【The invention's effect】
As described above, according to the dissimilar material determination method of the present invention, the noise characteristics are measured using the initial test material for each lot without using the reference material, and the noise characteristics are measured based on the measured noise characteristics. The value range is set, and for the test material thereafter, different materials are determined based on the comparison between the measured noise characteristic and the normal value range, so that operability can be improved and the test material between lots can be improved. Dissimilar materials can always be determined easily and reliably without being affected by component differences and the like.
Further, according to the apparatus for judging a different material according to the present invention, the noise characteristics of the test material can be measured using a flaw detection device using a leakage magnetic flux, so that it is simple and inexpensive.
[Brief description of the drawings]
FIG. 1 is a schematic view showing one embodiment of a dissimilar material judging device for performing a dissimilar material judging method according to the present invention.
FIG. 2 is a block diagram showing a detailed configuration of the dissimilar material determination device shown in FIG.
FIG. 3 is a schematic diagram showing details of a leakage magnetic flux detection unit.
FIG. 4 is a diagram illustrating the definition of noise characteristics.
FIG. 5 is a diagram illustrating a measurement example of background noise.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conveyance line 2 Test material 3 Leakage magnetic flux detection part 4 Noise characteristic measurement part 5 Judgment part 6 Control device 31 Electromagnet 32 Magnetoelectric conversion element 41 Band filter 42 Maximum value peak memory 43 Minimum value peak memory 44 Differentiator 51 Switch circuit 52 Normal Value range setting circuit 53 Judgment circuit

Claims (2)

Prior to determining a different material of a test material lot composed of magnetic materials having the same component and the same rolling chance, a background noise level of a leakage magnetic flux is measured in a longitudinal direction of the test material for at least one test material at an initial stage of the lot. Setting a normal value range of at least two noise characteristics of the maximum value, the minimum value, and the maximum value-minimum value from the measured noise level;
Thereafter, a maximum value, a minimum value, and a minimum value obtained from the noise level measured in the longitudinal direction for the other test materials, based on a comparison between at least two noise characteristics of the noise characteristics and the normal value range. A dissimilar material judging method characterized by judging a dissimilar material. A leakage magnetic flux detecting means for detecting the leakage magnetic flux and converting it into an electric signal;
From the output of the electrical signal, a band filter that cuts off the output due to the defect of the test material,
A noise characteristic measuring means for storing a maximum value and a minimum value of the noise level from the electric signal output after the cutoff and calculating a maximum value-minimum value from the maximum value and the minimum value to obtain each noise characteristic; ,
A normal value range setting means for setting a normal value range from any two or more noise characteristics of the obtained maximum value, minimum value, and maximum value-minimum value;
Determining means for determining a different material based on a comparison between the normal value range and two or more noise characteristics by the noise characteristic measuring means,
The normal value range setting means sets the normal value range based on the noise characteristics measured by the noise characteristic measuring means of at least one test material at the beginning of the test material lot having the same component and the same rolling chance. Control means for controlling the inspection material to determine a different material based on a comparison between the noise characteristic measured by the noise characteristic measurement means and the normal value range of the test material in the determination means. Dissimilar material determination device.

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