JPS61286745A - Apparatus for diagnosing embrittlement - Google Patents

Abstract

PURPOSE:To judge the embrittlement quantity of a member, by measuring polarizing characteristics with good accuracy by correcting a measuring error caused by a measuring cell or measuring temp. CONSTITUTION:The potential difference between a rotor 2 and the collimation electrode in a measuring cell 1 is controlled by a potentiostat 91 and potential is raised at a constant speed to be held for a definite time and, thereafter, said potential is reduced at a constant speed. At this time, the current between the opposed electrode of the measuring cell 1 and the rotor 2 is measured by the potentiostat 91. The current and voltage relating to this measurement are inputted to a polarizing characteristic operation apparatus 98 to calculate a re-passivity current which is, in turn, subsequently inputted to an embrittlement quantity operation apparatus 100. At this time, the re-passivity current has irregularity due to temp. and corrected to the value corresponding to reference temp. by a temp. correcting operation apparatus 97 and the relation between the re-passivity current and embrittlement quantity is corrected on the basis of the value represented by the cell 1 and the ratio of the capacity of an electrolyte and a measuring area by a measuring cell correcting operation apparatus 99. Because the embrittlement quantity is calculated from the corrected re-passivity current, real embrittlement quantity, from which temp. and the effect of the measuring cell were removed, appears in the output of the apparatus 100.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an embrittlement diagnostic device that non-destructively detects the amount of embrittlement over time in metal materials exposed to high temperatures for long periods of time, such as steam turbine components. The present invention relates to a embrittlement diagnostic device that measures embrittlement by

[Technical background of the invention and its problems]

Generally, polarization tests are performed to measure the corrosion resistance and stress corrosion cracking susceptibility of metal materials. Usually, as shown in the block diagram of FIG. 8, a sample 9 is placed in a specific electrolyte 5, and the potential between the reference electrode 3 and the sample 9 is adjusted by a potentiostat 91 connected to a scanner 92. In this test, the current flowing between the counter electrode 4 and the sample 9 is measured by a recorder 95 connected via a coulomb meter 93 or a logarithmic converter 94.

The test results of such a test are shown in the curve diagram of FIG. 9, for example. The figure shows the measurement results when the potential between the reference electrode 3 and the sample 9 was initially increased at a constant rate, held at a specific potential, and then decreased. By the way, it is known that when this polarization test is performed using a certain solution, a significant difference appears in the polarization characteristics between embrittled and non-embrittled materials. For example, the literature "New Nondestructive Aging Deterioration Diagnosis Technology for Steam Turbine Components" (by Kiyoshi Saito and 4 other authors, the actual state of deterioration and damage of structural metal materials and collection of papers from the Nondestructive Inspection Technology Symposium, Japan Nondestructive Inspection Association, (September 1982) explains this point in detail. In other words, low alloy steel (CrM) for steam turbine rotors
When a polarization test was conducted on a sound material and a tempered embrittlement material (oV steel), the results were shown in Figure 9, and the minimum value of current I, (repassivation current) and the amount of embrittlement were can be related. However, the amount of embrittlement is the upper height ΔFATT of the fracture surface transition temperature FATT. steam turbine 1
When a polarization test is conducted on martensitic stainless steel (12Cr steel) used in 4-temperature blades, the results are shown in the curve diagram in Figure 10, and the peak current ■ is also one of the embrittlement amounts. It can be related to a certain upper boric acid impact value.

Normally, a polarization test is performed by immersing the sample to be measured in an electrolytic solution as shown in Figure 8, but this polarization test can be performed non-destructively without cutting out the sample from the actual component and placing it in the electrolytic solution. It was published in Japanese Unexamined Patent Application Publication No. 59-815 that
This device is disclosed in Japanese Patent Application Laid-Open No. 57-142540, Japanese Patent Application Laid-Open No. 57-138051, and the like. So that polarization tests can be performed non-destructively,
These test devices have a measurement cell 1 as shown in the schematic diagram of FIG. 11, and measure polarization characteristics by pressing this against a turbine rotor 2, which is an object to be measured. As shown in the figure, the measuring cell 1 has an opening 8 surrounded by a packing 6, and the measuring cell 1 is filled with an electrolytic solution 5, and the current value between the reference electrode 3 and the counter electrode 4 is controlled by a potentiostat. The amount of embrittlement of the turbine rotor 2 is measured by measuring the temperature via the temperature measuring device 91 and the temperature measuring device 96 connected to the thermometer 7 .

However, these conventional test devices have the following disadvantages.

(1) The measured value depends on the measurement cell.

Because polarization tests measure the electrochemical properties of materials,
During the measurement, Fe'' is dissolved into the electrolyte. Then,
If the amount of Fe2+ is sufficiently small compared to the capacity of the electrolytic solution, the measurement results will hardly be affected by it. However, when m of Fe2+ is large compared to the amount of electrolyte, the measurement results are influenced by the color tube, resulting in variations and inaccuracies.

(2) The measured value depends on the measured temperature.

Measurement of polarization characteristics is performed non-destructively on blunt members that are used at high temperatures for long periods of time. For this reason, measurements are often performed at the site where the plant is installed, but the temperature at the time of measurement changes depending on the time of measurement. On the other hand, since the polarization property is an electrochemical property of the material, the rate of the chemical reaction depends on the temperature, which has been an obstacle to highly accurate measurement.

As described above, in the conventional embrittlement diagnostic device using the polarization test method, the measurement results are affected by the capacitance of the measurement cell and the temperature at the time of measurement, resulting in variations in the measurement results. Also the 9th
As shown in the curve diagram in the figure, the measured current ■ is the embrittlement m
It is difficult to accurately measure the absolute value of the fracture surface transition temperature 11FATT, which is necessary for diagnosing the reliability of actual machine parts, by simply showing ΔFATT, which has been an obstacle to improving the reliability of embrittlement diagnosis.

[Purpose of the invention]

Therefore, the purpose of the present invention is to reduce the measurement variations caused by the measurement cells of the conventional polarization test equipment and the measurement errors caused by the measurement temperature, to measure polarization characteristics with high accuracy, and to reduce the amount of embrittlement of parts. An object of the present invention is to provide an embrittlement diagnostic device that can accurately calculate the absolute value of the fracture surface transition temperature FATT and the upper boric acid impact value of the member.

[Summary of the invention]

In order to achieve the above object, the present invention provides a measurement cell having an opening facing a sample, filled with an electrolytic solution, and having a reference electrode and a counter electrode arranged therein, and a measurement cell having an opening facing the sample, and a measurement cell having a reference electrode and a counter electrode arranged therein. Embrittlement characterized by comprising a measuring means for applying a voltage and measuring the current value, and a means for calculating the amount of embrittlement of a sample based on preset conditions and an output signal of the measuring means. The present invention provides a diagnostic device.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embrittlement diagnostic device according to an embodiment of the present invention, which particularly illustrates a case where the device is applied to embrittlement measurement of a steam turbine rotor made of CrMoV low alloy steel. As shown in the figure, a measurement cell 1 is pressed and fixed against the surface of a rotor 2, which is an object to be measured. Measuring cell 1
For example, it has a structure as shown in the schematic diagram of FIG. 11. That is, the measuring cell 1 is filled with an electrolytic solution 5, and a counter electrode 4, a reference electrode 3, and a thermometer 7 are arranged.
It is configured so that it is in contact with The counter electrode 4 and reference electrode 3 are connected to a potentiostat 91. On the other hand, the potentiostat 91 is also connected to the rotor 2. The output of the thermometer 7 is connected to a temperature measuring device 96, and the signal from the temperature measuring device 96 is connected to a temperature correction calculation device 97. The output signal of the potentiostat 91 is connected to a polarization characteristic calculation device 98. The output signal of the polarization characteristic calculation device 98 is combined with the output signal of the temperature correction calculation device 97 and the output signal of the measurement cell correction calculation device 99 in the embrittlement diagnosis device 1.
Connected to 00.

The output signal of the embrittlement layer calculation device 100 is the impact characteristic calculation device N1.
01 to the output device 102.

Various setting data related to measurement are input to the setting data input device 103.
The setting data is sent to the impact characteristic calculation device 101 and the measurement cell correction calculation device 99.

In this configuration, its operation will be explained next.

The potentiostat 91 controls the potential difference between the rotor 2 and the reference electrode 3, increases the potential at a constant rate, holds the potential for a certain period of time, and conversely decreases the potential at a constant rate. The current flowing between the rotors 2 is measured by a potentiostat 91. The current and voltage related to this measurement are input to the polarization characteristic calculation unit @98 in time. The relationship between this current and voltage is as shown in the curve diagram in FIG. Minimum value of current 1. (Re-immobility!21 current) is calculated by the polarization characteristic calculation device ff198, and the embrittlement amount calculation device 1
00 is input.

The amount of embrittlement ΔFATT and the repassivation current Ir have a relationship as shown in the characteristic diagram of FIG. 2. However, this relationship depends on the temperature T
is a constant temperature T. Moreover, this holds true when the amount of Fe2+ eluted from the measurement sample is sufficiently smaller than (2) of the electrolytic solution 5. On the other hand, when diagnosing embrittlement of structural parts of a plant, measurements must be performed on-site, and the measured hot water temperature T is not necessarily a constant lagoonal temperature T. It is not.

Furthermore, in order to make measurement possible at any location of the actual structure, it is necessary to make the measurement cell 1 as small as possible.

Therefore, it is difficult to obtain a sufficiently large electrolyte black for the amount of Fe2+ dissolved into the electrolyte 5 during measurement.

The repassivation current measured at temperature T is 1. This value includes variations due to temperature.

The temperature correction FA calculation device 97 calculates this current 1. of! S quasi-temperature T
The action of correcting o to the value I0 is performed.

On the other hand, the measurement cell correction calculation device 99 corrects the relationship (evaluation curve) between the re-FII state current and the amount of embrittlement using a value representative of the measurement cell 1, that is, the capacity/area ratio of the electrolyte container ■ and the measurement area Δ. and temperature-compensated re-passive current■. The amount of embrittlement ΔFATT is calculated from

The amount of embrittlement calculated by the embrittlement diagnosis device 100, that is, the increase ΔFATT in the fracture surface transition temperature FATT is input to the impact property calculation device 101. The impact property calculation device 101 first calculates the fracture surface transition temperature FATT at the time of manufacture of the object to be measured, the chemical composition of the material, and the mechanical properties at the time of manufacture (tensile strength, etc.).
Calculate using. Next, the fracture surface transition temperature FAT during manufacturing
The increase amount ΔFATT is added to T to obtain the current fracture surface transition temperature FATT. The setting data input device @103 is used to input and set the chemical components and mechanical properties necessary to determine the fracture surface transition temperature FATT during manufacturing, as well as the open area A of the measurement cell and the volume of the electrolyte solution. Impact characteristic calculation device 1
01 and is sent to the measurement cell correction calculation device 99.

The output device 102 outputs a polarization curve as shown in FIG. 9 obtained as a result of polarization characteristic measurement, an embrittlement level ΔFATT, and a fracture surface transition temperature FATT.

The thermometer 7 inserted into the measurement cell 1 may be of any type as long as it can be used within the range of measurement temperature changes and can output temperature electrically; for example, a thermometer, an electrical resistance thermometer, etc. may be used. Ru.

Here, a specific method of humidity correction by the temperature correction calculation device 97 will be explained.

When the capacitance/area ratio V/A of the measurement cell 1 is infinite, the repassivation current, which is a polarization characteristic, changes with respect to the measurement temperature T as shown in the characteristic diagram of FIG. 3.

Therefore, by using the characteristics shown in FIG. 3, it can be determined which curve of ΔFΔ-rT lies on the measured value I with respect to temperature T. If this curve is ΔF A T' T i , then the reference temperature T. The repassivation current for l. can be found.

However, this ΔFATT is an apparent value that includes the influence of the V/A of the measurement cell, and also includes the influence of the capacitance/area ratio V/A, which is the representative value of the measurement cell 1. be. Therefore, further correction is required to remove the influence of measurement cell 1.

Therefore, next, a method of correcting errors caused by the measurement cell 1 will be explained.

Fe2+, which is dissolved into the solution during the measurement of polarization characteristics, is caused by the fact that when the measurement cell 1 is pressed against the measurement object, the electrolyte 5
, that is, it is proportional to the measurement area A. Therefore, the ratio between the volume of Fe2+ dissolved in the electrolytic solution 5 during measurement and the volume of the electrolytic solution 5 can be expressed as the volume ffi/area ratio V/A of the volume V of the electrolytic solution 5 to the measurement area. I can do it.

Figure 4 shows the reference temperature T. 817 is a characteristic diagram showing the relationship between the repassivation current (■) and the embrittlement jΔFATT using the area ratio (■/Δ) as a parameter.

In other words, the capacity/area ratio V/A is a constant value S. If it is larger, the evaluation curve becomes one curve, and if it is smaller, the evaluation curve changes depending on the value. The measurement cell correction calculation device 99 uses the temperature/area ratio V/A, which is the representative value of the measurement cell 1 and is output from the setting data input device 103, and calculates the value using the temperature correction calculation device 97 on the curve shown in FIG. The repassivating current I. Find the embrittlement difference ΔFATT.

The embrittlement envelope ΔFA and T-T obtained as above are the true embrittlement envelope ΔFAT with the influence of temperature T and measurement cell 1 removed.
It is T.

Next, a method of calculating the fracture surface transition temperature FATT during manufacturing using the impact property calculation device 101 will be described.

The fracture transition temperature FATT of a material is correlated with its chemical composition and mechanical properties. In this example, we focused on this point, and calculated the fracture surface transition temperature FATT during material manufacture using a regression equation between the weight percentage of each chemical component of the material and mechanical properties (tensile strength, elongation, yield strength, etc.). Calculated by That is, the weight percent and mechanical properties of each chemical component are x,
< r = 1 to n), and the corresponding regression coefficient is 8° (
i=o-n), the fracture surface transition temperature FATT during manufacturing
can be calculated using the following formula.

FATT=B + Σ B・X・・・・・・・(
1) 0, 11 1 = where B is a regression coefficient, X is an independent variable, and for specific purposes is a coefficient representing the weight basis 1- of each chemical component and mechanical properties. Incidentally, the regression coefficient B is determined by performing regression analysis on a material whose fracture surface transition temperature FATT is known in advance.

As mentioned above, in this example, the measured temperature A') 3111
By correcting the variation in the polarization characteristic value caused by a constant cell, it is possible to obtain a highly reliable polarization characteristic with much better charge accumulation than in the past. Therefore, an accurate value can be obtained as the embrittlement stiffness ΔFATT calculated using these polarization characteristic values. In addition, conventionally, it was common to simply output a polarization curve as a polarization characteristic measurement result, but with the configuration of this embodiment, the embrittlement temperature ΔFATT and fracture surface transition temperature FATT @ calculated are directly necessary for design and maintenance. It can be used immediately for maintenance management as it is outputted as an image.

Next, the present invention was applied to martensitic stainless steel (12C
A case will be described in which the present invention is applied to a high-temperature rotor blade of a steam turbine made of steel. Like the rotor, the high-temperature rotor blades of a steam turbine are used for long periods of time at high temperatures (over 500°C).
Brittleness occurs over time, and it is necessary to periodically grasp the period of embrittlement.

However, in the case of 12Cr steel, the polarization curve becomes as shown in the curve diagram in Fig. 10, and the peak current ■ is determined by p v in Fig. 5 with respect to the upper nitric acid impact value E.
The relationship is as shown in the shelf characteristic diagram. Therefore, the polarization characteristic calculation device 98 detects this peak current I and inputs it to the embrittlement 5 calculation device @100. The embrittlement diagnostic device 100 detects the peak current ■ in FIG. The upper nitric acid impact value Evshelf5helf is calculated from the relationship between the upper nitric acid impact value Evshelf and the upper nitric acid impact value E.

At this time, temperature correction is applied to the peak current ip by the temperature correction calculation device 99, and correction is performed by the measurement cell 1 to correct the temperature difference and the variation caused by the measurement cell 1. The same is true for . However, in the case of CrMOV low alloy steel, temperature correction uses the relationship between current I and temperature T in Figure 3, but 12C
In the case of r steel, the peak current I as shown in the characteristic diagram in Figure 6
, and temperature T.

Further, the measurement cell 1 is corrected by correcting the evaluation curve using the value of the volume fa/area ratio V/Δ, as shown in the characteristic diagram of FIG.

In addition, in the case of a turbine rotor, the increase in the fracture surface transition temperature FATT is set by 1q as embrittlement progresses, whereas in the case of high-temperature rotor blades, the absolute value Evshelf of the upper nitric acid impact value is required as embrittlement progress. Therefore, W-impact calculation device 1
01 is the upper shelf IIi calculated by the embrittlement diagnosis device 100!
ms value Evsゎ. 1. is sent as is to the output device 102. The setting data input device 103 inputs only the measurement surface V4A of the measurement cell 1 and the volume ff1V of the electrolytic solution 5, and the output device 1
02 is the polarization curve, peak current I 1 upper shelf area siege value Ev
Output shelf.

In this case, as in the example for the turbine rotor, the polarization characteristics are determined by correcting for variations caused by temperature and measurement cells, so the upper nitric The impact value E can be obtained.

vshelf (Effects of the Invention) As described above, according to the present invention, when determining the aging embrittlement of metal materials by non-destructive measurement, temperature differences, which conventionally were simply considered as variations in measured values, can be Regarding errors caused by errors and errors caused by the measurement cell, clarify the relationship between the temperature difference and polarization characteristics and the representative value of the measurement cell, that is, the relationship between the ratio of measurement area and electrolyte capacity and polarization characteristics, and use these relationships. Since the polarization characteristics are determined by adding appropriate corrections, it is possible to obtain polarization characteristics with much higher accuracy than conventional methods.
As a result, a highly reliable embrittlement diagnostic device can be obtained even during embrittlement.

In addition, the present invention not only obtains a polarization curve as a test result, but also focuses on the unique relationship between polarization characteristics and embrittlement m, and calculates the embrittlement level △FATT or upper nitric acid impact value. An embrittlement diagnostic device that makes it possible to calculate E vsshelf has been realized.

On the other hand, when applying the present invention to CrMOV low-alloy steel, the relationship between the chemical composition and mechanical properties and the fracture surface transition temperature FATT at the time of manufacturing the component, and the absolute value of the current fracture surface transition temperature FATT from ΔFATT. Since the value can be determined, it can greatly contribute to the maintenance and management of structures that are used for long periods of time at high temperatures, where there is concern that they may become brittle over time.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embrittlement diagnostic device according to an embodiment of the present invention, and FIG. 2 shows embrittlement mΔFATT and re-alil state current (2). Figure 3 is a characteristic diagram showing the relationship between the measured hot water temperature T and the re-passive state current ■, and Figure 4 is a characteristic diagram showing the relationship between the measured cell fit/area ratio V/A and the re-passive current S.
A characteristic diagram showing the relationship between the current I and Figure 5 shows the relationship between the peak R current and the upper boric acid impact value Evshe.
Figure 6 is a characteristic diagram showing the relationship between temperature T and peak current ■, Figure 7 is a characteristic diagram showing the relationship between capacitance/area ratio V/A of measurement cell 1 and peak current ■. Figure 8 is a block diagram of a conventional polarization test device, Figure 9 is a characteristic diagram of C
FIG. 10 is a curve diagram showing an example of a polarization curve for rMoV low alloy steel; FIG. 10 is a curve diagram showing an example of a polarization curve for 12Cr steel; FIG. 11 is a layout diagram showing an example of a measurement cell. 1... Measuring cell, 2... Turbine rotor, 3...
Reference electrode, 4... Counter electrode, 5... Electrolyte, 6... Packing, 7... Thermometer, 91... Potentiostat, 96... Temperature measuring device, 97... Temperature correction Calculation device, 98... Polarization characteristic calculation device, 99... Measurement cell correction calculation device, 100... Embrittlement amount calculation device, 101
... Impact characteristic calculation device, 102 ... Output device, 10
3...Setting data input device. Applicant's representative Kiyoshi Inomata Figure 2 Measured temperature aT Figure 3 Figure 4 Figure 5 Figure 9 Potential Y Figure 10

Claims (1)

[Claims] 1. A measurement cell having an opening facing the sample, filled with an electrolytic solution, and having a reference electrode and a counter electrode arranged therein, and applying a voltage functionally between the reference electrode and the counter electrode. An embrittlement diagnostic device comprising: a measuring means for measuring the current value at the same time; and means for calculating the amount of embrittlement of the sample based on preset conditions and an output signal of the measuring means. 2. The embrittlement diagnostic device according to claim 1, wherein the measuring means includes means for measuring the temperature of the electrolytic solution, and the means provides a temperature correction signal to the calculating means. 3. The calculation means inputs the measurement cell opening area and the amount of electrolyte as preset conditions, and corrects the calculation result based on the ratio of each amount. The embrittlement diagnostic device described in section. 4. The calculation means is characterized in that an initial value of the amount of embrittlement determined by the components and properties of the sample is inputted as a preset condition, and the absolute embrittlement state of the sample is calculated. An embrittlement diagnostic device according to claim 1.