JP2559401B2 - Degradation inspection method for metal - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for inspecting deterioration of a metal material, and more particularly to a ferrite-containing stainless steel and the like used in a high temperature environment of a chemical plant and a nuclear plant. The present invention relates to a measurement suitable for detecting high temperature aging embrittlement damage of a metal material actual machine member.

[Conventional technology]

As an example of a conventional embrittlement measuring method, JP-A-54-61981
There is a method as described in the issue. Here, the presence or absence of embrittlement of the austenitic stainless steel weld metal is determined by the fact that the initial amount of δ-ferrite has decreased by 5% or more.

[Problems to be solved by the invention]

Among metallic materials used at high temperatures, it is already known that aging embrittlement occurs when used at high temperature for a long time, particularly in the case of ferrite-containing stainless steel. This is because σ phase embrittlement due to precipitation of σ phase occurs at a relatively high temperature of about 600 ° C. or higher, and so-called 475 ° C. brittleness occurs in the range of 400 ° C. to 500 ° C. However, 475 ° C brittleness may occur during long-term use even in the temperature range of 400 ° C or lower, and sufficient consideration must be given to the use of ferrite-containing stainless steel actual machine components at high temperatures.

However, the above-mentioned prior art does not consider brittleness at 500 ° C or lower, and cannot detect the degree of 475 ° C brittleness.

In addition, the initial amount of ferrite in the welded portion of the actual machine differs depending on the welding position, and has a large variation. Furthermore, since the number of welding spots is enormous in an actual machine, it is difficult to monitor the amount of ferrite in all welded portions. Therefore, there is a problem that the conventional technique cannot be applied to a portion where the initial ferrite amount is unknown.

On the other hand, as an example of the eddy current test method (hereinafter referred to as ECT), there is JP-A-55-141653 "deterioration state determination method for strong precipitation hardening type iron-based alloy". In this conventional example, the deterioration state of the iron-based alloy, the ECT value of the initial measurement material, the material to be measured before use or a material of the same kind of material as the initial heat treatment of the material to be measured ECT
It shows a method of comparing values and determining whether the values are positive or negative.

However, quantitative determination cannot be performed because the determination is made only by positive or negative.

An object of the present invention is to provide a method capable of nondestructively and accurately detecting the degree of embrittlement of an actual member of a metallic material such as a ferrite-containing stainless steel used in a high temperature environment.

[Means for solving problems]

Paying attention to the fact that the electrical characteristics of metal materials change with use at high temperatures for a long time, using an AC bridge, the absolute value and phase angle of the unbalanced voltage of the measured object relative to the reference, and the hardness of the metal material. The present invention proposes a method for inspecting deterioration of a metal material, which determines the degree of embrittlement of the metal material by comparing changes in mechanical properties such as structure.

 Specifically, two measurement methods are proposed.

First, in the first method, the unbalanced voltage of the AC bridge of the deteriorated material with respect to the reference is measured, and the unbalanced voltage of the deteriorated material in the initial state is estimated from this unbalanced voltage. The degree of deterioration of the metal material is calculated from the amount of change between the initially estimated unbalanced voltage and the measured unbalanced voltage of the deteriorated material. By changing the measurement frequency and performing the same evaluation, the certainty accuracy of the degree of deterioration is improved.

On the other hand, in the second method, a part of the surface of the deteriorated material is subjected to a process such as etching and the information of the structure is taken by the replica method or the like to estimate the unbalanced voltage in the initial state of the deteriorated material. The degree of deterioration of the metallic material is calculated from the amount of change between the initial estimated unbalanced voltage and the unbalanced voltage of the deteriorated material.

In any method, the determination result of the deteriorated material is quantitative.

[Action]

When a metal material is used in a high temperature environment for a long time, the internal structure of the metal material changes, and the strength of the metal material decreases. Along with this, it can be seen that the electrical properties of the metal material, such as the electrical resistivity ρ and the magnetic permeability μ, and the mechanical properties such as hardness and metal structure change.
For example, as a result of various studies on embrittlement of ferrite-containing stainless steel due to high temperature heating,
Since there is a certain correlation between the unbalanced voltage of the, the brittleness of metallic materials such as ferritic stainless steel, in particular, the absolute value of the unbalanced voltage of the deteriorated material can be used by utilizing this relationship. By estimating the initial state of the deteriorated material from the value of the phase angle, the value of the phase angle, and the information of the metal structure obtained by the replica method or the like, the degree of progress of embrittlement can be accurately detected.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of a system configuration for carrying out the deterioration inspection method for a metal material according to the present invention. In the figure, reference numeral 1 is a pipe used in a nuclear power plant or the like, which is an object to be measured. Also, 2A and 2B are probe coils, 3
Is a scan drive device, 4 is a scan drive control device, 5 is an eddy current flaw detector, 6 is a computer, 7 is an external storage device, 8 is an external recording device, 100 is a data processing device, and 200 is a metal internal tissue observation device. 210 is a hardness measuring device. DUT 1
A probe coil 2A is arranged on the surface of the test piece 11, and a probe coil 2B is arranged on the surface of the reference test piece 11.

 The details of the scanning drive device 3 are shown in FIG.

On the outer circumference of the pipe 1 to be measured, a moving ring 30
The moving ring 30 is provided with a driving mechanism including a driving wheel 41, an auxiliary wheel 36, a connecting shaft 40, a motor 36, a belt 35 and a gear sensor 39 at 120 ° intervals. Drive wheel 41
Via belt 35 stepping motor with encoder 36
Driven by. The drive wheel 41 is fixed to the connecting shaft 40 and attached to the outer peripheral ring 30. Auxiliary wheels 34 are provided on the other side of the connection shaft 40, and drive wheels 41
The auxiliary wheel 34 and the auxiliary wheel 34 are pressed against the pipe 1 with an appropriate force within the range of elastic deformation of the connecting shaft 40. Outer ring 30
Attitude control of three gear cap sensors 39
It is arranged just above 40 to detect and correct the twist state of the outer peripheral ring 30. The outer ring 30 has a fixed rod 31
A fixed ring 32 is attached to the fixed ring 32, and a rotary ring 33 that rotates in contact with the fixed ring 32 is provided inside the fixed ring 32. The inner surface of the rotating ring 33 has a rack structure and is rotated by a motor 37 having a pinion gear 38. The rotating ring 33 has
Cylinder 20 with coil 2A and hardness meter 21 for measuring hardness
0, polishing device 121 for polishing the surface, etching processing device 140
A surface observing device consisting of a surface treatment device consisting of, a light source 201 and a video camera 202 having a zoom function is attached. This is a mechanism that can move on the surface of the pipe.

The details of the cylinder portion 20 for moving the coil 2A up and down are shown in FIG. The probe coil 2A is pressed against the DUT 1 by a motor 23 via a ball screw mechanism 22. This pressing force is detected by the load cell 21. The vertical movement amount of the coil is detected by the gear sensor 24. The probe coil can be moved in the circumferential direction by the rotating ring 33, and can be moved in the axial direction of the outer peripheral ring 30.

Details of the polishing device 121 are shown in FIG. Rotary polishing head 1
26 is rotated by a motor 123 via a connecting lever 122. The connecting lever 122 is operated by a cylinder 124 which is driven in an orthogonal direction, is pressed against the surface of the DUT 1, and can polish the surface. The polishing device 121 can be moved in the circumferential direction by the rotating ring 33.

The details of the etching device 140 are shown in FIG. A cell 143 for etching the surface of the DUT 1 is provided with a rubber-like substance 142 at the end in contact with the DUT 1.
43 is being sealed. The cell 143 is pressed by a cylinder 145 with a load cell 147 at a constant pressure. In cell 143,
The etching liquid 150 and the neutralizing liquid 151 are selected by the switching valve 149 and supplied by the pump 148. The cylinder 145 is fixed to the rotating ring 33 and can move in the circumferential direction.

Details of the tissue observation apparatus 200 are shown in FIG. The tissue observation device 200 includes a video camera 202 having a light source 201 and a magnifying glass 203.
And a jig 204 for fixing these to the rotating ring 33.
The rotating ring 33 enables movement in the circumferential direction.

Details of the hardness measuring device 210 are shown in FIG. The indenter 211 is provided at the tip of a shaft 214 having a load cell 212.
The shaft 214 is moved up and down by a motor 215 by a ball screw mechanism 213. The displacement of the indenter 211 can be measured by the gear sensor 216.
The hardness measuring device 210 is fixed to the rotating ring and is movable in the circumferential direction.

The probe coil 2A is arranged on the surface of the DUT 1, and the probe coil 2B is arranged on the surface of the reference test piece 11.

The motor and other driving units of the scan drive device 3 and a signal system are connected to the scan drive control device 4 and are controlled by the scan drive control device 4.

The two probe coils have a coil shape of 3 mm in diameter and 70 turns.
The one with turns is embedded in an insulating resin and has the same characteristics. These probe coils are connected to the eddy current flaw detector 5 having an AC bridge circuit and equivalently form the circuit shown in FIG.

The eddy current flaw detector 5 has an automatic balancing function in the frequency range DC to 5 MHz. Here, the absolute value and the phase angle of the measured unbalanced voltage are converted into a digital signal and taken into the computer 6.

The computer 6 controls the drive control device 4, the eddy current flaw detector 5, the external storage device 7, and the external recording device 8 via the interface. Here, 16 bit CP for computer 6
The U is used and a floppy disk is connected as the external storage device 7 by a parallel interface. In addition, the drive control device 4 is connected via a peripheral interface adapter (PIA), and the eddy current flaw detector 5 is connected to the GP-IB.
It is designed to exchange data via an interface.

Further, the polishing device 121 and the etching processing device 140 are controlled by the drive control device 4, and the observation result of the metallographic structure and the data such as hardness are processed by the data processing device 100 and taken into the computer 6.

Now, the main routine for executing the measuring method of the present invention in the system configured as described above will be described with reference to the flow chart of FIG.

First, the drive unit 3 is arranged on the surface of the DUT 1 such as the piping of the nuclear reactor, and the drive unit 3 is set at the origin of the measurement system.
Therefore, the inspection range for aging deterioration and the measuring method described later are selected and input from the computer 6. When the measurement is started, the drive device 3 moves to the measurement start point, measures the eddy current according to the input measurement method, and performs one of the three evaluations. After the measurement is completed, the driving device 3 moves to the next measurement position. The inspection is repeated in the same manner, and is continued until the drive device 3 reaches the final position. The data being measured is stored in the floppy disk 7. After the measurement is completed, the measurement data is fetched again from the floppy disk 7 into the computer 6.
This data is processed by a data processing method corresponding to the previously specified measurement method, and becomes a judgment material for aging embrittlement. The result is output to the external recording device 8 or displayed on the CRT of the computer.

FIG. 9 is a flow chart showing the data collection stage of the ECT, which shows the details in the step of FIG. Here, first, the frequency is determined. Next, the probe coil 2B is pressed against an arbitrary reference test piece 11 to balance it, and then the probe coil 2B is lifted off (lifted), the lift-off signal is set to a phase angle of 0 °, and the cancel is performed. Measure the offset value to be measured. Transducer coil 2A
Is pressed against the outer surface of the pipe (object to be measured) 1, the probe coils 2A and 2B are switched, and the absolute value of the unbalance voltage and the phase angle are measured by the eddy current flaw detector 5. This data is stored in the floppy disk 7 via the computer 6. After that, the frequency Δ is increased and the routine is repeated again. When the frequency reaches the final frequency, the measurement is finished and the data processing is started.

Although it has been stated that the measurement data is temporarily stored in the floppy disk, if the internal memory such as DRAM in the computer 6 has sufficient capacity, it may be stored there.
Needless to say, the speed of data processing in the next stage is increased. It is also possible to use a large capacity hard disk.

Details of the evaluation 1 corresponding to the steps of FIG. 8 will be described with reference to FIGS. 10 to 13.

FIG. 10 is an evaluation flow chart of only the ECT signal, and shows the step of FIG. 8 in detail. The measurement position, the absolute value of the unbalanced voltage, and the phase angle data stored in the floppy disk 7 are loaded into the computer 6.

By the way, according to the deterioration test of the material, the unbalanced voltage of the virgin material changes its absolute value due to the dispersion of the material as shown in FIG. 11, but in the direction of the constant phase angle θ ₁ at a specific frequency. Appeared. Further, the deterioration of the material appears in the direction of the phase angle θ ₂ , and the degree of deterioration corresponds well to the difference ΔV between the unbalanced voltage of the virgin material and the unbalanced voltage after deterioration.

Therefore, as shown in FIG. 12, from the measured unbalanced voltage of the deteriorated material, the intersection point of the deterioration direction vector and the vector direction of the virgin material is obtained, and this is taken as the initial estimated value Vs of the deterioration, and Vs and the deterioration material The unbalance voltage difference ΔV is obtained. As for the correspondence between the unbalance voltage ΔV of deterioration and the strength of the material, as shown in FIG. 13, the deterioration master curve of the initial estimated value Vs is obtained in advance, and this is used to calculate the strength of the material corresponding to ΔV. (For example
K _IC ) is calculated. After performing the above-described evaluation according to the flow chart of FIG. 10, the measured position and the evaluated value are output to the external recording device 8, and the same routine is repeated for other measured positions.

Next, the details of the observation and evaluation of the tissue corresponding to the steps and in FIG. 8 will be described with reference to FIGS. 14 to 18.

FIG. 14 is a flow chart for examining the internal tissue of the step of FIG.

The inspection position is read, the polishing apparatus 121 is moved, and the measured object 2 is polished for a constant polishing time Ktime. After the polishing is completed, the etching device 140 is moved to the same position to etch the polishing position for a certain time Ktime. After the etching process, the observation device 202 performs image processing on the metal structure to calculate the area ratio of the phases. The result is stored in the memory.

After the surface of the DUT 1 is processed by the surface processing device, the metal structure data can be measured by a surface observation device such as a replica or an ultrasonic microscope. An example of this state is shown in FIG. 2 as in Figure 16
In the case of having a phase metallographic structure, at high temperature aging of 500 ° C or less, there is no significant change in the metallographic structure, so from the area ratio of the precipitation structure to the matrix structure or the crystal grain size,
The initial physical properties of deterioration can be estimated.

FIG. 15 shows a detailed flow chart of the step evaluation 2 of FIG.

The unbalanced voltage and the tissue area ratio of the deteriorated material are read from the memory. By adopting a master curve as shown in Fig. 17 in the virgin material, the initial state of the deteriorated material can be easily estimated. From Fig. 18, the initial unbalance voltage Vs of the deteriorated material obtained
And the soft equilibrium voltage of the deteriorated material, the difference ΔV can be obtained, and the degree of deterioration of the metal material can be evaluated according to FIG. 13 as described above.

Hardness and evaluation 3 corresponding to step and in FIG.
Will be described in detail with reference to FIGS. 19 to 23.

FIG. 19 is a flow chart for measuring the hardness of the step shown in FIG.

Read the inspection position and move the device. The indenter 211 is pressed and the hardness is measured.

FIG. 20 is a detailed flow chart of the step of FIG.

In the experiment, it was confirmed that the relationship between the unbalanced voltage and the hardness tended to be as shown in Fig. 21 with aging deterioration. That is, the deterioration of the material is estimated from the two parameters that change with the deterioration. As shown in FIG. 22, the value of the deteriorated material is extended in the deterioration direction, and the position intersecting the curve of the virgin material is set as an initial estimated value H ₀ , and the difference from the deteriorated material is represented by a parameter x ₀ . From the values of x ₀ and H ₀ , the degree of deterioration of the deteriorated material can be evaluated from the relationship between the strength and the parameter x ₀ obtained in advance (FIG. 23).

〔The invention's effect〕

According to the present invention, since the degree of embrittlement of a metal material used at high temperature can be detected nondestructively and quickly, it is possible to prevent embrittlement damage in advance and enhance the safety of an actual machine. You can

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention, and FIG. 2 is
FIG. 3 is a perspective view of a pipe measuring apparatus according to an embodiment of the present invention.
FIG. 4 is a perspective view of the probe coil pressing mechanism in FIG. 2, FIG. 4 is a perspective view of the polishing device in FIG. 2, and FIG. 5 is a perspective view of the etching processing device in FIG. Fig. 6 is a perspective view of the observation device in Fig. 2, Fig. 7 is a perspective view of the hardness measuring device in Fig. 2, and Fig. 8 is a main operation routine of the embodiment of the present invention. Flow chart, FIG. 9 is a flow chart for ECT measurement in FIG. 8, FIG. 10 is a flow chart for evaluation 1 in FIG. 8, and FIGS. 11 to 13 are FIG. FIG. 14 is a graph chart for explaining in the flow chart of FIG. 14, FIG. 14 is a flow chart for inspecting the internal tissue in the embodiment of the present invention, FIG. 15 is a flow chart for evaluation 2 in FIG. To FIG. 18 are explanatory views for explaining the flow chart of FIG. 15, FIG. 19 is a flow chart of hardness measurement in FIG. 8, and FIG. Evaluation 3 in Figure 8
21 is a flow chart for explaining the flow chart of FIG. 20, and FIG. 24 is an equivalent circuit diagram of an eddy current flaw detector. 1 ... Object to be measured, 2A, 2B ... Probe coil, 3 ... Scan drive device, 4 ... Scan drive controller, 5 ... Eddy current flaw detector, 6 ... Computer, 7 ... External storage Device, 8 ……
Recording device, 11 ... Standard test piece, 100 ... Data processing device, 121 ... Polishing device, 140 ... Etching processing device, 20
0 …… Tissue observation device, 201 …… Light source, 202 …… Video camera, 210 …… Hardness measuring device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Sugano No. 502 Jinrachicho, Tsuchiura-shi, Hitachi Ltd. Machinery Research Laboratory (72) Inventor Hideyo Saito 3-1-1 Sachimachi, Hitachi-Hitate Co., Ltd. (56) References JP-A-60-225058 (JP, A) JP-A-59-183359 (JP, A) JP-A-61-62858 (JP, A)

Claims (2)

(57) [Claims] 1. A method for inspecting deterioration of a metal material by an eddy current flaw detection method, wherein an AC signal is applied to a measured object of a metal material and a reference test piece, and an eddy current generated in them is detected by an AC bridge circuit. A specific reference test piece is selected, and data of the unbalanced voltage and the phase angle of the AC bridge circuit are collected while changing the frequency of the AC signal between the reference test piece and the device under test.
Using the step and the phase angle as the deterioration information obtained in advance from the relationship between the virgin material and the deteriorated material of the measured object, the data of the unbalanced voltage and the phase angle of the measured object measured in the A step are used as the basis. The B step for estimating the unbalanced voltage and the phase angle in the initial state of the measured object, the unbalanced voltage and the phase angle in the initial state of the measured object estimated in the B step, the unbalanced voltage measured in the A step, and A metal material comprising: a difference in the vector amount from the phase angle; and a C step for calculating the strength of the object to be measured using a calibration curve of the above-mentioned vector amount difference-metal material strength. Deterioration inspection method. 2. The B step for estimating the unbalanced voltage and the phase angle in the initial state of the object to be measured according to claim 1, is the crystal grain size related to the metallic structure of the object to be measured or the area ratio of the phase. Therefore, a step for estimating the unbalanced voltage and the phase angle in the initial state of the measured object is used by using the calibration curve of the metallographic structure-electrical characteristics obtained in advance from the relationship between the virgin material and the deteriorated material of the measured object. A method for inspecting deterioration of a metal material, which is characterized in that