JPH08278287A - Method and device for diagnosing steel material heat history - Google Patents

Abstract

PURPOSE: To reduce an inspection site on periodical inspection and at the same time secure the reliability for judging deterioration conditions and reduce and rationalize the periodical inspection by finding a non-sound part out of a number of steel materials to be diagnosed and precisely inspecting only the non-sound part. CONSTITUTION: A coil 2 is brought into contact with a steel material 10 to be diagnosed where static magnetic field is applied and pulse current is fed to the coil 2 to generate eddy current on the surface of the steel material 10. The detection sensitivity of electromagnetic ultrasonic waves is amplified and at the same time sensitivity amplification factor is displayed, the change in the specific permeability of the steel material 10 is obtained from the sensitivity amplification factor, and the heat history of the steel material 10 is diagnosed according to the change in the specific permeability. Namely, the steel material 10 is diagnosed as a non-sound part with a high-temperature scale-generation heat history when the change in the specific permeability is equal to or more than a specific value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to deterioration management of steel materials exposed to high temperatures, such as boiler heat transfer tubes, and particularly suitable for extracting and diagnosing deteriorated parts (unhealthy parts) in periodic inspections. The present invention relates to a history diagnosis method and a diagnosis device.

[0002]

2. Description of the Related Art Boiler heat transfer tubes are exposed to high temperature combustion gas during operation, so that deterioration phenomena due to high temperature creep, high temperature corrosion or high temperature fatigue occur. This deterioration phenomenon is
In steel materials such as boiler heat transfer tubes including low alloy steel and low carbon steel, the metal temperature is remarkably generated upon receiving a heat history of 500 to 600 ° C. Conventionally, metal thermometers were installed every few tubes in the width direction of the boiler heat transfer tube in the non-heating part, and the heat history of the boiler heat transfer tube that had been received so far was managed by operation. This is a method for diagnosing heat history, and even for the same boiler heat transfer tube, local overheating caused by local adhesion of scale inside and outside the tube and overheat status of the boiler heat transfer tube without metal thermometer are diagnosed. I couldn't. Therefore, the deterioration phenomenon of these boiler heat transfer tubes was managed by judging from the metal structure of the boiler heat transfer tubes at any place based on experience during non-destructive inspections, based on experience during regular inspections. .

In the conventional method for diagnosing heat history of steel products, nondestructive inspection is conducted by empirically determining samples from many inspection points to manage the steel products deteriorated by heat history without diagnosing sound or unhealthy parts. Therefore, if the sample does not hit the unhealthy part, there is a risk that the judgment of the deterioration state is erroneous.

[0004]

In the conventional method for diagnosing heat history of steel products, a sample is empirically determined from many inspection points without diagnosing a sound part or a non-health part of a steel product having a heat history. Since the sample is subjected to nondestructive inspection, there is a problem that the deterioration state is erroneously judged unless the sample hits the unhealthy portion.

An object of the present invention is to provide a steel material heat history diagnosis method and a diagnosis apparatus capable of finding an unhealthy portion deteriorated by heat history from a large number of steel materials to be diagnosed.

[0006]

In order to achieve the above object, a method for diagnosing a steel material thermal history according to the present invention applies a static magnetic field to a steel material to be diagnosed whose relative magnetic permeability has changed due to thermal history and applies a coil. In contact with each other, a pulse current is applied to the coil to generate an eddy current on the surface of the steel to be diagnosed, and the eddy current density that changes according to the relative permeability is detected by electromagnetic ultrasonic sensitivity and displayed by the sensitivity amplification factor, and the sensitivity amplification The relative magnetic permeability is obtained from the coefficient to diagnose the thermal history.

The steel material to be diagnosed may be so constructed as to be diagnosed as an unhealthy portion having a high temperature or a thermal history of scale formation when the relative permeability changes by a predetermined value or more.

In the steel material heat history diagnosing device, a permanent magnet for generating a static magnetic field is used in any one of the steel material heat history diagnosing methods, and a coil attached to the permanent magnet and abutting on a steel material to be diagnosed. A pulser that applies a pulse current to the coil to generate an eddy current in the steel to be diagnosed, an amplifier that amplifies the detected electromagnetic ultrasonic sensitivity, a display that displays the sensitivity amplification factor, and a diagnosis based on the sensitivity amplification factor. And a means for diagnosing the thermal history by obtaining the relative permeability of the steel material.

Further, in the heat history management method for a boiler heat transfer tube, the above-mentioned steel material heat history diagnosis device is brought into contact with at least one boiler heat transfer tube having a heat history, and the relative magnetic permeability changes to a predetermined value or more and becomes unhealthy. Each boiler heat transfer tube diagnosed as a part is non-destructively inspected, and the result of the non-destructive inspection is recorded to manage deterioration of each boiler heat transfer tube due to thermal history.

[0010]

As shown in FIG. 2, the relative magnetic permeability of the boiler heat transfer tube made of steel material, for example, low carbon steel, is 500 to 600 ° C. which is the metal temperature.
It has the property of changing greatly over time. The penetration depth δ of the eddy current generated by bringing the coil closer to the steel material to which the static magnetic field is applied and passing a pulse current through the coil changes depending on the relative permeability as shown in the formula (1).

[0011]

[Equation 1]

That is, when the relative permeability increases, the penetration depth of the eddy current becomes shallow and the eddy current density becomes high. When the eddy current density changes while the static magnetic field is applied, the Lorentz force changes, and this change in Lorentz force changes the amplitude of vibration on the surface of the boiler heat transfer tube, resulting in changes in electromagnetic ultrasonic waves. .

Therefore, since the heat history of the boiler heat transfer tube is detected as a change in relative permeability, that is, a change in sensitivity of electromagnetic ultrasonic waves, by applying an electromagnetic ultrasonic sensor to the boiler heat transfer tube, the individual boiler heat transfer tubes can be detected. It becomes possible to diagnose the heat history of the part.

When the metal temperature of the boiler heat transfer tube exceeds 600 ° C., scale (Fe ₃ O ₄ ) is produced on the outer surface of the tube. This scale is an insulator but a ferromagnet,
When a static magnetic field is applied, the ferromagnetic film acts to strengthen the magnetic field in the metal of the boiler heat transfer tube, so that the Lorentz force increases and the electromagnetic ultrasonic wave detection sensitivity increases. Therefore, according to the present embodiment, not only the metal temperature of the boiler heat transfer tube is in the range of 500 to 600 ° C., but also the heat history can be managed in a wide range of 600 ° C. or higher including the scale generation phenomenon.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the steel material thermal history diagnosis method applies a static magnetic field 7 to the steel material to be diagnosed 10 whose relative magnetic permeability has changed due to thermal history, abuts the coil 2, and applies a pulse current to the coil 2 to perform the diagnosis. An eddy current is generated on the surface of the steel material 10, the eddy current density changed according to the relative magnetic permeability is detected by electromagnetic ultrasonic sensitivity and displayed by the sensitivity amplification factor 5, and the relative permeability is calculated from the sensitivity amplification factor 5. It is configured to diagnose the heat history of the steel material 10 to be diagnosed, and the steel material to be diagnosed is to be diagnosed as an unhealthy portion having a heat history of high temperature or scale formation when the change in relative permeability exceeds a predetermined value.

Next, the operation of the embodiment will be described. During the periodic inspection, after the electromagnetic ultrasonic sensor 11 including the permanent magnet 1 and the coil 2 is brought into contact with the steel material 10 to be diagnosed such as a boiler heat transfer tube, a pulse current is passed from the pulsar 3 to the coil 2 to make the steel material 10 to be diagnosed. Generates an eddy current on the surface of. 500-600
As shown in FIG. 2, the steel material to be diagnosed 10 exposed to a high temperature of ℃ has a relative magnetic permeability of, for example, 500 μ or more. When the relative magnetic permeability becomes large, the eddy current becomes The permeation depth becomes shallow and the eddy current density increases. When the eddy current density changes, the Lorentz force F changes, and the amplitude of ultrasonic vibration on the surface of the steel 10 to be diagnosed changes as shown by A in the figure. As a result, the sensitivity amplification factor is displayed on the display device 6 as a change in the sensitivity of the electromagnetic ultrasonic wave. Therefore, by determining the relative permeability from the sensitivity amplification factor, the steel material 10 to be diagnosed has a high temperature or 600
It can be diagnosed that it is an unhealthy part having a heat history of scale generation of ℃ or more. By collecting the sump from the steel to be diagnosed and examining the metal structure by nondestructive inspection, it is possible to diagnose the deteriorated state of the unhealthy portion of the entire steel to be diagnosed that has undergone a high-temperature heat history.

According to the present invention, it is possible to find a deteriorated portion (non-healthy portion) of the boiler heat transfer tube from many boiler heat transfer tubes by the heat history diagnosis of the boiler heat transfer tube, and to periodically check only the deteriorated portion. It is possible to perform various precise inspections, reduce inspection parts during regular inspections, and ensure high reliability of thermal history. In other words, it is possible to perform highly reliable inspection with a minimum of precision inspection, which has the effect of shortening and rationalizing the periodic inspection period.

As shown in FIG. 1, a steel material heat history diagnosing device according to another embodiment of the present invention is used in the steel material heat history diagnosing method, and includes a permanent magnet 1 for generating a static magnetic field 7 and a permanent magnet 1. Coil 2 attached and abutted on the steel 10 to be diagnosed
A pulser 3 that generates a eddy current in the steel 10 to be diagnosed by applying a pulse current to the coil 2, an amplifier 4 that amplifies the detected electromagnetic ultrasonic sensitivity, and a display device 6 that displays the sensitivity amplification factor 5. It is configured by means for obtaining the relative magnetic permeability of the steel material 10 to be diagnosed from the sensitivity amplification factor 5 and diagnosing the thermal history, for example, the relative magnetic permeability graph shown in FIG.

That is, an electromagnetic ultrasonic sensor 11 is formed by the permanent magnet 1 and the coil 2, an electromagnetic ultrasonic detecting device is formed by adding the pulsar 3 and the amplifier 4, and a display device 6 is added to the electromagnetic ultrasonic detecting device. Then, a steel material heat history diagnostic device is configured.

According to this embodiment, since the electromagnetic ultrasonic sensor is brought into contact with the steel material to be diagnosed and the thermal history of the steel material to be diagnosed can be diagnosed from the display of the sensitivity amplification factor, the unhealthy portion can be easily and accurately found. There is an effect.

As another embodiment of the present invention, a method for managing heat history of a boiler heat transfer tube is as follows. As shown in FIG. 1, at least one boiler heat transfer tube having a heat history is installed in the steel material heat history diagnostic device. Steel material) 10 and the relative magnetic permeability has changed to a predetermined value or more and each boiler heat transfer tube 10 that has been diagnosed as an unhealthy portion is non-destructively inspected, and the results of the non-destructive inspection are recorded to record the boiler heat transfer tubes. It is configured to manage the deterioration due to the heat history of.

According to the present embodiment, since the deteriorated boiler heat transfer tube is found out of a large number of boiler heat transfer tubes and the boiler heat transfer tube is precisely inspected, it is possible to accurately grasp the deterioration state, so This has the effect of shortening the inspection period and streamlining regular inspections.

[0023]

According to the present invention, an unhealthy portion is found out of a large number of steel materials to be diagnosed, and a precise inspection of only the unhealthy portion is carried out, whereby the number of inspected portions at the time of the periodic inspection can be reduced and deterioration is caused. There is an effect that the reliability of the judgment of the situation can be secured and the inspection period can be shortened and rationalized.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a graph illustrating relative permeability.

[Explanation of symbols]

 1 permanent magnet 2 coil 3 pulser 4 amplifier 5 sensitivity amplification factor 6 display device 7 static magnetic field 10 steel to be diagnosed

Claims (4)

[Claims] 1. A static magnetic field is applied to a steel material to be diagnosed whose relative magnetic permeability has changed due to thermal history, a coil is brought into contact with the steel material, and a pulse current is applied to the coil to generate an eddy current on the surface of the steel material to be diagnosed. The eddy current density changed according to the relative permeability is detected by electromagnetic ultrasonic sensitivity and displayed by the sensitivity amplification factor, and the thermal history is diagnosed by obtaining the relative permeability from the sensitivity amplification factor. Steel material heat history diagnosis method. 2. The steel material according to claim 1, wherein the steel material to be diagnosed is diagnosed as an unhealthy portion having a high temperature or a thermal history of scale formation when the relative permeability changes by a predetermined value or more. Thermal history diagnosis method. 3. A method for diagnosing a steel material thermal history according to claim 2, wherein a permanent magnet for generating a static magnetic field, a coil attached to the permanent magnet and abutting on a steel material to be diagnosed, and a pulse for the coil. A pulser that applies an electric current to generate an eddy current in the steel material to be diagnosed, an amplifier that amplifies the detected electromagnetic ultrasonic sensitivity, a display device that displays the sensitivity amplification factor thereof, and a display device that displays the sensitivity amplification factor of the steel material to be diagnosed from the sensitivity amplification factor. A steel material thermal history diagnostic device, comprising: means for diagnosing thermal history by obtaining relative permeability. 4. A steel material heat history diagnostic device according to claim 3,
A non-destructive inspection is performed on each boiler heat transfer tube that is in contact with at least one boiler heat transfer tube having a heat history, and the relative permeability has changed to a predetermined value or more and is diagnosed as an unhealthy portion, and the result of the nondestructive inspection is recorded. A heat history management method for a boiler heat transfer tube, characterized in that deterioration of each boiler heat transfer tube due to heat history is managed.