JPS626154A - Carburization measuring probe - Google Patents

Abstract

PURPOSE:To measure not only depth of a carburized part but also the carburized part having an expanse by providing the first Hall element so as to run roughly along the direction of a line of magnetic force, and providing the second Hall element in the vicinity of a magnetic pole of the magnet. CONSTITUTION:In case a carburized part 16 having an expanse in the inside of a tube 15 exists, when a probe 10 approaches, a line of magnetic force of a magnet 12 is influenced by a high magnetic permeability of the carburized part 16 and attracted strongly, and an inclination is generated in the line of magnetic force passing through the Hall element 13. Therefore, an output waveform of the Hall element 13 becomes that which has raised an electromotive voltage in both end parts of the carburized part 16. On the other hand, when the line of magnetic force is attracted strongly by the carburized part 16, a magnetic flux density of a Hall element 14 being in the vicinity of a magnetic pole of the magnet increases. Accordingly, when the elctromotive voltage of the Hall element 14 shows a prescribed level or above, it is decided that the carburized part 16 having an expanse exists in its position, and also an area of its carburized part 16 can be decided.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is used for carburization measurement, which is used when non-destructively measuring carburized parts generated on the inner surface of cracking tubes for ethylene production in the petrochemical industry from the outer surface. It concerns probes.

<Prior art> ASTM HK40 (0.4%C-
25%Cr-20%Ni), Hr'45 (0,
45%C-25%Cr-35%Ni), or HP improving material (IP material with MOlW, Nb, etc. added singly or in combination), etc. are used.

When a cranking tube is used for a long period of time, carbon generated by reaction adheres to the inner surface of the tube, and this adhered carbon diffuses into the metal at high temperatures, causing carburization. Carbon infiltrated by carburization forms Cr carbide, and when carburization is accelerated, the Cr carbide becomes coarse, leading to a significant decrease in ductility at low temperatures (approximately 800°C or less), and thermal expansion of the carburized portion of the tube. The coefficient is smaller than that of the non-carburized part, so if the tube is heated and cooled rapidly, the generation of tensile and compressive stress and the decrease in ductility in the low temperature range may occur, causing the tube to break. Ta.

Therefore, in order to prevent tube destruction and maintain safe and smooth operations, it is necessary to conduct carburization inspections periodically to accurately understand the presence or absence of carburization and its progress. .

As a non-destructive method for measuring the carburization depth, there are various magnetic measurement methods that utilize changes in the composition of the carburized part, that is, changes in magnetic properties due to Cr deficiency and relative increases in Fe and Ni. Are known. For example, there is a method of measuring the carburized depth of a tube by electromagnetic induction, a method of using a Gauss meter that applies the ball effect, etc.

As shown in FIG. 7, the measurement method using a Gaussmeter is to apply a probe 3 containing a Hall element 2 connected to a Gaussmeter main body l to the outer surface of a tube 4, which is a material to be tested, and to form a carburized portion 5 on the inner surface. If there is, the depth of the carburized part 5 is measured by detecting the Hall electromotive force generated when the lines of magnetic force of the residual magnetism of the carburized part 5 cross the Hall element 2. However, the residual magnetic flux density of the carburized part is too small (about 2 to 3 gauss for HP material), and it is not possible to accurately measure the carburized depth if it is slightly larger than the earth's magnetic field.

On the other hand, the carburization depth measurement results obtained by electromagnetic induction method,
When compared with the actual measurement results from destructive testing, II K 4
Although a relatively good response was obtained for tubes made of 0 material, the measurements for tubes made of IP material or HP improved material had large variations and lacked reliability.

This is due to the decarburized layer formed on the outer surface of the tube 4 made of IIP material or IP improved material. ) 6, decarburization and Cr removal occur, and the magnetic permeability of that portion increases. That is, when these tubes 4 are used for a long time at high temperatures, even if no carburization occurs on the inner surface of the tube, a decarburized layer (layer depth of about 50 to 500 μ+a) 6 forms on the outer surface. This is because when the depth of the groove is large, a high indicated value is indicated, and this indicated value is mistaken for carburization.

Therefore, when measuring the presence or absence and depth of the carburized portion 5 of the tube 4, it is necessary to first remove the decarburized layer 6 on the outer surface of the tube 4 with a grinder, etc., and then remeasure and evaluate. is the reality.

Therefore, even if the number of locations to be measured is small, if a large number of locations are to be measured, a large amount of time must be spent, which poses many problems in terms of practicality.

Therefore, the applicant has already proposed a technique that allows simple and quick measurement of the decarburized layer 6 without grinding it. That is, as shown in FIG. 8, this is arranged in a magnetic field between the permanent magnet 7 and the N pole and S pole of this permanent magnet 7 so as to be substantially parallel to the permanent magnet 7. A probe 9 equipped with a Hall element 8 is used. In this case, when the probe 9 approaches the carburized part 5, the magnetic field of the permanent magnet 7 is influenced by the carburized part 5, and the magnetic field line crosses the Hall element 8 diagonally as shown by the dotted line. The carburized portion 5 on the inner surface of the tube 4 is determined based on the electromotive force generated.

Therefore, if the decarburized layer 6 partially exists on the outer surface of the tube 4, the magnetic flux distribution of the permanent magnet 7 will change due to the influence of the decarburized N6, but the decarburized layer 6 is present over the entire outer surface of the tube 4. Since the magnetic field of the permanent magnet 7 is changed by this, the lines of magnetic force do not cross the Hall element 8 diagonally. In other words, unless there is a carburized part 5,
The lines of magnetic force passing through the Hall element 8 remain parallel to the Hall element 8, and no electromotive force is generated in the Hall element 8.
Therefore, the decarburized layer 6 will not be mistaken as the carburized layer 5.

<Problems to be Solved by the Invention> However, when using the probe 3.9 having such a configuration, in the center of the part where the carburized part 5 has a wide spread, the magnetic field lines passing through the Hall element 8 are Element 8
Since the voltage becomes parallel to the output voltage and the electromotive voltage of the output becomes zero, there is a problem that it becomes impossible to make a determination. That is, at both ends of the carburized portion 5, the lines of magnetic force cross obliquely with respect to the Hall element 8, so that the output waveform t of the electromotive force of the Hall element 8 becomes as shown in FIG. However, this is the same as the output waveform when there are two locally carburized parts 5 as shown in Fig. It was not possible to distinguish between cases where there is a 5.

In view of these problems, the present invention provides a novel carburization measuring probe that can determine the depth and range of a carburized portion.

Means for Solving the Problems> As a first specific means for solving the above problems, the present invention comprises a magnet and a Hall element disposed within the magnetic field of the magnet. In a carburized measurement probe that measures a carburized part by changes in magnetic lines of force caused by the carburized part inside the material to be inspected, there is a probe on the side of the material to be inspected of the magnet and on the side of the center between a pair of magnetic poles that corresponds to the direction of the lines of magnetic force. A first Hall element is provided approximately along the same side as the first Hall element, and a second Hall element is provided on the same side of the magnet as the first Hall element and near the magnetic pole of the magnet so that the magnetic flux density increases when the carburized portion approaches. As a second specific means, the method includes a magnet and a Hall element placed in the magnetic field of the magnet, and measures the carburized portion by changes in magnetic lines of force due to the carburized portion inside the material to be inspected. In the probe for carburization measurement, a first Hall element is provided on the test material side of the magnet and on the center side between the pair of magnetic poles so as to be substantially along the direction of the magnetic lines of force, and the first Hall element is provided with respect to the magnet. A second Hall element is provided on the same side as the Hall element and near the magnetic pole of the magnet so that the magnetic flux density increases when the carburized part approaches, and a second Hall element is provided on the same side as the Hall element and on the opposite side of the magnet with respect to the second Hall element. A third Hall element is provided on the third Hall element, and the magnetic field on the third Hall element side is approximately equivalent to the magnetic field on the second Hall element side in a portion of the test material that does not have a carburized part.
A dummy piece is provided near the Hall element.

Effect> When the first Hall element 13 approaches the carburized part 16 when measuring the carburized part 16 of the tube 15, the lines of magnetic force of the magnet 12 cross diagonally with respect to the first Hall element 13, and as its output, the carburized part 16 An electromotive force is generated that correlates to the depth of the

Further, when the carburized portion 16 has a spread, the first Hall element 13 generates an output at both ends thereof. On the other hand, since the magnetic flux density of the lines of magnetic force passing through the second Hall element 14 increases if the carburized portion 16 exists, the electromotive voltage thereof also increases. Therefore, from the outputs of these Hall elements 13 and 14, not only the depth but also the area of the carburized portion 16 can be determined.

In the proof lO having the dummy piece 18 and the third Hall element 19, the third Hall element 19 has a carburized portion 16.
Since a considerable amount of electromotive voltage is generated, by offsetting this from the output of the second Hall element 14, the influence of the decarburized layer 17 is reduced.

<Example> Hereinafter, the present invention will be described in detail with regard to the illustrated example.
As shown in the figure, this carburization measurement probe 10 includes a permanent magnet 12, a first Hall element 13, and a second Hall element 13 in a protective container 11.
A Hall element 14 is provided. The magnet 12 is rod-shaped, and the trough king tube (test material) 15 of this magnet 12
On the side, a first Hall element 13 is provided so as to be located approximately in the center between the magnetic poles N-5, and a second Hall element 14 is provided near one of the magnetic poles of the magnet 12, respectively. Hall element 1
3.14 both have a flat plate shape, and when a current is passed in a direction perpendicular to the magnetic field in the thickness direction, an electromotive force is generated in the direction perpendicular to the magnetic field and current. . The first Hall element 13 is provided parallel to the magnet 12 and substantially along the lines of magnetic force of the magnet 12 during normal operation.

Further, the second Hall element 14 is parallel to the magnet 12 like the first Hall element 13, and the lines of magnetic force of the magnet 12 cross the second Hall element 14 in a substantially perpendicular direction even in normal times. Sometimes the magnetic flux density is provided to further increase. The protective container 11 is made of non-magnetic material. Note that each Hall element 13, 14 is connected to a Gaussmeter main body (not shown).

When measuring the carburized portion 16 of the cranking tube 15 using the probe 10 configured as described above, the probe 10 is
0 is applied to the outer surface of the tube 15, and the probe 10 is scanned in the axial direction and circumferential direction of the tube 15.

When the tube 15 does not have the carburized portion 16, the magnetic field of the magnet 12 is not disturbed, so that lines of magnetic force are distributed approximately parallel to the magnet 12 in the center between the magnetic poles N-3. Therefore, since the lines of magnetic force that cross the first Hall element 13 are approximately parallel, the output of the electromotive voltage shows a constant value of zero or a low level.On the other hand, the lines of magnetic force that cross the second Hall element 14 are perpendicular to each other. However, since only the thin decarburized layer 17 exists instead of the carburized portion 16, the concentration of magnetic lines of force is low and the increase in magnetic flux density is low, so the electromotive voltage of the second Hall element 14 exhibits a substantially constant value. Therefore, these Hall elements 13.
14 indicates that the carburized portion 16 does not exist.

When a carburized portion 16 with a wide spread exists inside the tube 15, when the probe lO approaches, the lines of magnetic force of the magnet 12 are strongly attracted due to the influence of the high magnetic permeability of the carburized portion 16, so that the first Hall element 13 There is a slope in the magnetic field lines that pass through.

Therefore, the output waveform of the first Hall element 13 is as shown in FIG.
As shown in the figure, the electromotive force rises at both ends of the carburized portion 16. On the other hand, when the magnetic lines of force are strongly attracted by the carburized part 16, the magnetic flux density of the second Hall element 14 near the magnetic pole of the magnet increases as shown in FIG. 2, and the electromotive force of the second Hall element 14 increases accordingly. growing.

Therefore, Figure 3A.

As shown in B, there are two places where the electromotive force of the first Hall element 13 rises, and between them
When the electromotive force of No. 4 shows a predetermined level or higher, it is known that a carburized portion 16 with a spread exists at that position, and the area of the carburized portion 16 can also be determined. Note that the carburization depth in this case is correlated with the waveform high value of the output of the first Hall element 13, and the carburization depth can be determined from this.

In the above configuration, the magnetic flux density of the magnetic lines of force passing through the second Hall element 14 changes depending on the presence or absence of the carburized portion 16 in the tube 15, but the decarburized layer 17 exhibiting high magnetic permeability also has an influence. If the depth of the decarburized layer 17 differs depending on the location, the electromotive voltage of the second Hall element 14 may change gradually depending on the decarburized layer 17. Furthermore, in the case of a long tube 15, the degree of decarburization differs between the burner side and the anti-burner side, so the output of the second Hall element 14 changes.

Therefore, in order to eliminate the influence of such a decarburized layer 17, as shown in FIG. A device connected to the Hall element 14 so that the electromotive force is canceled out is used.

The dummy piece 18 has substantially the same magnetic permeability as the part other than the carburized part 16 of the tube 15, for example, the decarburized layer 20.
It is also possible to cut a part of the cranking tube and use it, or a completely different member may be used. This dummy piece 18 is attached to the tube 1 against the magnet 12.
5, equidistant from the tube 15 (d1
= d2). Third Hall element 1
9 is the same as the second Hall element 14, and the magnet 12
It is arranged near the N pole of the second Hall element 14 with respect to the magnet 12, so that the magnetic field on the third Hall element 19 side is affected by the carburized part because there is a dummy piece. Second Hall element 1 in the part of the tube 15 without 20
This is approximately equivalent to the magnetic field on the 4th side. This third Hall element 19
are connected in opposite directions to the second Hall element 14 so that the electromotive voltages cancel each other out.

In the probe 10 having such a configuration, the tube 1
In the part of No. 5 where the carburized portion 16 is not present, the electromotive voltages of the second Hall element 14 and the third Hall element 19 are at approximately the same level, and the output from the terminal 21 obtained by canceling them out is almost zero. The value is close to .

If the carburized portion 16 is present, the magnetic flux density of the lines of magnetic force passing through the second Hall element 14 becomes large, as described above. Furthermore, on the third Hall element 19 side, the magnetic lines of force of the magnet 12 are strongly attracted to the carburized part 16 side, which has high permeability and a large cross-sectional area, so although there is a dummy piece 18, the magnetic flux density passing through this third Hall element 19 is It will decrease slightly. As a result, the electromotive voltages of the second Hall element 14 and the third Hall element 19 have waveforms such as A and H shown in FIG.
As shown in the figure C, the influence of the decarburized layer 17 of the tube 15 is removed, and the carburized portion 16 becomes conspicuous.

The magnetic permeability of the dummy piece 18 needs to be changed in accordance with the conditions of the material to be measured, such as when the heating temperature is high and the decarburization depth is large. Therefore, the protective container 11
If the dummy piece 18 is provided in a detachable manner, the versatility of the probe 10 can be obtained.

The second Hall element 14 and the third Hall element 19 may be provided near different magnetic poles of the magnet 12, respectively, as shown in FIG.

In addition to connecting the second Hall element 14 and the third Hall element 19 in opposite directions, the outputs of the respective electromotive voltages may be input into a subtractor or the like to electrically cancel each other out.

An electromagnet may be used instead of the permanent magnet 12. Further, the shape, structure, etc. of the magnet 12 are not particularly limited, and can be arbitrarily changed in design depending on the material to be inspected.

A plurality of probes 10 may be provided in the circumferential direction of the tube 15.

<Effects of the Invention> According to the present invention, in addition to providing the first Hall element so as to be substantially along the direction of the magnetic lines of force of the magnet, the magnetic flux density increases when the carburized part approaches the first Hall element on the same side and near the magnetic pole of the magnet. A second Hall element is provided to ensure that the carburized area is wide, and these Hall elements are used in combination, so it is possible to measure not only the depth of the carburized area, but also the carburized area that has a wide area. This improves the measurement accuracy of the carburized part, making it possible to determine the area of the carburized part.

Further, according to the present invention, the second Hall element is provided separately from the second Hall element, and the magnetic field on the second Hall element side is the same as the magnetic field on the second Hall element side in a portion of the test material that does not have a carburized part. Since the dummy piece is provided so that the output is approximately equivalent to that of the carburized part, it is possible to eliminate the influence of parts other than the carburized part by the output of the second Hall element and the third Hall element, and it is possible to perform reliable measurements. It has the advantage of being easy and quick to perform.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. 2 is an explanatory diagram of the same operation, FIG. 3 is a waveform diagram of the same, FIG. 6 is a sectional view showing another embodiment, FIG. 7 is a configuration diagram showing a conventional example, and FIG. 8 is a diagram showing the same waveform.
The figure is a configuration diagram showing another conventional example, Figure 9 is a waveform diagram, and Figure 10 is a waveform diagram.
The figure is a cross-sectional view of the tube. 10...Probe, 12...Permanent magnet, 13...
First Hall element, 14...Second Hall element, 15...
・Cracking tube, 16... Carburized part, 17...
- Decarburized layer, 18... dummy piece, 19... third Hall element.

Claims (1)

[Claims] 1. For carburization measurement, comprising a magnet and a Hall element disposed within the magnetic field of the magnet, and measuring the carburized portion by changes in magnetic lines of force caused by the carburized portion inside the material to be inspected. In the probe, a first Hall element is provided on the test material side of the magnet and on the center side between the pair of magnetic poles so as to be substantially along the direction of the magnetic lines of force, and on the same side of the magnet as the first Hall element. A probe for measuring carburization, characterized in that a second Hall element is provided near the magnetic pole of the magnet so that the magnetic flux density increases when the carburized part approaches. 2. In a probe for carburization measurement, which is equipped with a magnet and a Hall element placed in the magnetic field of the magnet, and measures the carburized portion by changes in the lines of magnetic force caused by the carburized portion inside the material to be inspected. A first Hall element is provided on the inspection material side and on the center side between the pair of magnetic poles so as to be substantially along the direction of the lines of magnetic force, and on the same side of the magnet as the first Hall element and near the magnetic poles of the magnet. , a second Hall element is provided so that the magnetic flux density increases when the carburized part approaches, a third Hall element is provided near the magnetic pole of the magnet and on the opposite side of the second Hall element to the magnet, and the third Hall element is provided so that the magnetic flux density increases when the carburized part approaches. A carburizing method characterized in that a dummy piece is provided near the third Hall element so that the magnetic field on the element side is approximately equivalent to the magnetic field on the second Hall element side in a portion of the material to be inspected that does not have a carburized part. Probe for measurement.