JPS63134934A - Method and device for diagnosing deterioration - Google Patents

Abstract

PURPOSE:To execute the non-destructive inspection of a member such as a stud, etc., by comparing the variation quantity of hardness after use against hardness before use of a member to be measured, with a variation quantity characteristic curve derived in advance with regard to the standard sample of the same member. CONSTITUTION:A probe 6 is inserted into the hole 2 of a stud 1 consisting of a first tooth 4 to be engaged to a screw and a screw part, being a member to be measured, and a constant-current power source 30 is applied. In the probe 6, contacts 8-1, 8-2, 8-3 and 8-4 which can be protruded and moved backward to both right and left sides by springs 7-1, 7-2, 7-3 and 7-4, respectively are arranged in the upper and lower directions, and the constant-current power source 30, and a voltmeter 9 are connected to the contacts 8-1, 8-4, and the contacts 8-2, 8-3, respectively. In this state, by comparing the measured value of the voltmenter 9 with the characteristic value of a hardness us electric characteristic of a standard sample derived in advance, by a hardness conversion device 10, the hardness of the inside surface of the hole 2 is measured.

Description

Detailed Description of the Invention <Industrial Application Field> ° This invention is applicable to steam turbines, turbine rotors, etc., which are used for long periods of time under tensile stress at high temperatures, or used for long periods of time under constant load. The present invention relates to a method and apparatus for diagnosing deterioration of members.

Technical background: For example, implanted parts used in steam turbines, turbine rotors, etc. are used at high temperatures and under tensile stress, so they develop creep strain and eventually break when used for a long time. It becomes like this.

For example, in the case of a stud bolt, the place where it breaks is the 6th point.
This is the "first threaded tooth" 4 shown in Figure (a), and this stud bolt remains in the implanted state even when it is opened for regular inspection (Figure 6 (b). )) are dangerous areas.

When diagnosing the deterioration state of implanted members such as stud bolts that have such breakage-prone areas, conventionally the only method has been to use non-destructive flaw detection to check for the presence or absence of cracks. However, in the case of members, especially stud bolts, the accuracy of non-destructive flaw detection is poor and is not practical enough.

In addition, generally, members that are used for long periods of time under a constant load tend to become brittle, so if they are not replaced before cracks occur, safety problems may occur. Therefore, it is necessary to non-destructively discover the crack occurrence site immediately before the crack occurrence as much as possible.

However, conventionally, there has been no method for non-destructively diagnosing the deterioration state of a member to be measured that meets such requirements.

<Problems to be Solved by the Invention> The present invention solves the problem of parts such as steam turbines and turbine rotors that are used at high temperatures and subjected to long-term tensile stress, or members that are used for long periods of time under constant load. The present invention aims to provide a deterioration diagnosis method for measuring the state of deterioration.

Further, the present invention aims to provide an apparatus capable of carrying out the above-mentioned deterioration diagnosis method.

Means for Solving the Problems In order to achieve the above-mentioned problem, the inventors of the present invention have conducted various experiments and found that the quality of the material changes when it is used at high temperatures for a long period of time. The degree of the change increases as the stress increases. For example, Cr
-Mo When the o-V material is heated for a long time, its hardness changes as shown in curve C in Figure 7 (However, the characteristic curve in Figure 7 is a parameter that combines both heating temperature T and heating time t. To summarize, the change expressed as a ratio to the initial hardness can be approximately approximated by a single curve.

In addition, the change in hardness when creep (applying stress at high temperature) is organized using parameters that combine the three factors of temperature, time, and stress, resulting in the characteristic curve MD shown in Figure 8.
become that way.

From these results, the timing of creep crack generation can be estimated by measuring changes in hardness. For example, a case where the temperature and time of use are known, but the initial hardness and stress are unknown is shown in FIG. 9 (at (b) (cl (di)).

In this way, it is conceivable to display changes in material quality as amounts that can be measured non-destructively, such as hardness, and perform maintenance management based on the amount of change.

However, in the case of high-temperature members, it is extremely difficult to estimate usage history such as temperature and stress, and the method of estimating the deterioration state of the member from the characteristic curve shown in FIG. 9 cannot be applied.

Therefore, a large number of bolts that had been used for a long period of time were sampled and analyzed by cutting to investigate the occurrence of cracks or the hardness of the corresponding locations. An example of the survey results is shown in Figure 10. The figure shows the temperature and
The time parameter is determined and the hardness at the same position is plotted against it, and the curve shows that bolts in actual use soften with long-term use, and bolts with cracks soften.

From these results, it is possible to estimate when creep cracks will occur in a used member from the amount of change in the hardness of the member. For example, the relationship between the temperature and time of use of the member are known, but the initial hardness before use and stress is unknown is shown in Figure 9 (al (bl (cl (di)).

FIG. 9fa) is a characteristic diagram showing the temperature during use of the member, the use time parameter G, and the ratio of initial hardness Hv0 to hardness HV during use (HV/HV0) at a high temperature and low stress position, that is, the degree of softening. Figure 9 (bl is a characteristic diagram showing the degree of softening at the remaining life evaluation position of the same member at a high temperature and high stress position, and Figure 9 (cl is a characteristic diagram showing the softening degree of the same member at the remaining life evaluation position) and ΔG (extra). Figure 9(d) is a characteristic diagram showing the relationship between the Larson and Mira parameters (Larson
-MillerParameter) T (C+Io
g tr) is a creep rupture characteristic diagram showing the relationship between stress σ generated in a member and stress σ. Based on the idea that the creep breakage occurring in the member and the remaining life can be estimated from these characteristic diagrams, we conducted research and were able to complete this invention.

Moreover, the change in hardness of a member is a typical physical property change value that represents a change in material quality, and instead of hardness, the physical properties of the base, such as changes in electrical resistance, also change, so these change values can also be used to determine the change in material properties. The degree of deterioration can be diagnosed.

That is, in the deterioration diagnosis method for a member of the present invention, the amount of change in hardness after use from the hardness before use on the inner surface of a hole formed in the member to be measured is determined in advance for a standard sample that is the same as the member to be measured. This method is characterized in that the degree of deterioration of the member to be measured is determined by comparing the characteristic curve values of the hardness before use and the hardness after use.

The hole formed in the member to be measured is a hole formed in the member to be measured, for example, when the member to be measured is a stud bolt 1 in a steam turbine, a turbine rotor, etc.
etc., the first
As shown in FIG. 1(a), since the hole 2 is in communication, it is possible to estimate the hardness of the deteriorated and breakage-prone part from the change in the hardness of the inner wall surface of the hole at the length position corresponding to the deteriorated and breakage-prone part. It has been experimentally confirmed that there is not much difference between the hardness of the deteriorated and breakage-prone area and the hardness of the inner wall of the stud bolt hole when measured at the same longitudinal position. Needless to say, the change in hardness in the longitudinal direction of the measuring member is greater.

Measurement examples are shown in FIGS. 11(a) and 11(b).

In FIG. 11 fa), the position where the Vickers hardness is high is at a low operating temperature, and it is considered that most stud bolts maintain their initial value Hv0.

Based on the above, as shown in Fig. 12, the hardness distribution was measured in the longitudinal direction of the bolt at the wall of the bolt center hole, and the minimum hardness value H
V and maximum value town. The softening degree α a == Hv/HVo can be determined from . Other than hardness, for example, electrical resistance can be found in the same way.

However, the center hole diameter of the bolt is approximately 10 to 30 mm, and cannot be measured with a commercially available hardness meter. That is, an ultra-small hardness meter or an alternative device method is required.

In this invention, an apparatus for carrying out the above-described method for diagnosing deterioration of a member includes a contact element that is attached to the tip of a par that can be pushed into the inner surface of a hole and is disposed so as to be able to suppress the inner surface of the hole, and a hole that is detected by the contact element. The hardness of the inner surface is determined as a change in the amount of push of the wedge that pushes out the contact, or as a change in the electrical resistance value according to the hardness of the inner surface of the hole detected by the contact. The method is characterized in that the degree of deterioration of the member to be measured is measured by comparing the hardness determined by the change in the amount of wedge indentation or the characteristic value of the hardness versus the Ti electrical resistance value.

As described above, the contact is pushed into the large circle formed inside the part to be measured, and the change in the hardness or electrical resistance value of the inner surface of the hole to be detected and the change in the material of the same material as the part to be measured are detected in advance. The desired degree of deterioration of the inner surface of the hole can be immediately diagnosed by comparing the hardness vs. electrical resistance value or the hardness vs. wedge penetration amount characteristic value measured for a standard sample consisting of:

Embodiments Next, typical embodiments of an apparatus used to carry out the deterioration diagnosis method of the present invention will be described.

Embodiment 1 FIG. 1 is a cross-sectional view of a main part showing the state of use of a deterioration diagnostic device that measures the degree of deterioration of a member to be measured based on a change in electrical resistance value between gauge points A and B.

In the figure, 6 is a probe formed to be able to be pushed into the hole 2 of the member to be measured 1a, and the probe 6 has a spring 7-
1. ? -2, 7-3, 7-4 contacts 8-1.8-2.8-3.8 that can be protruded and retracted on both the left and right sides respectively
-4 are arranged in the vertical direction, and the contacts 8-1 and 8-
4 is connected to a constant current power source, and contacts 8-2 and 8-3 are connected to a voltmeter 9. Then, the voltage value measured by the voltmeter 9 is compared in advance with the characteristic value obtained for the relationship between the hardness HV and the voltage characteristic of the member to be measured 2ζ using the hardness conversion M10, and the structure is such that the hardness of the inner surface of the hole can be directly connected. ing.

According to experimental results, it has been confirmed that the electrical resistance of the inner surface of the hole changes in a manner similar to the change in hardness when the member is used for a long period of time.

Example-2 FIG. 2 shows a second embodiment of the diagnostic device.

This device generates a wedge 12 using hydraulic pressure in a hydraulic pressure generating tank 11.
The contactor 13 is configured to be able to expand and contract in the outer circumferential direction in response to the raising and lowering of the wedge 12, and the diamond 14 at the tip of the contactor 13 is pressed against the inner surface of the hole to measure hardness. ing. The force with which the diamond F14 at the tip of the contactor 13 is pressed is determined by the amount by which the wedge 13 is pushed. The pushing amount of the wedge is determined by the vertical movement of a movable iron plate 16 fixed to the tip of the wedge that moves inside the differential transformer 15 constituting the wedge position sensor.
The degree of deterioration of the part to be measured can be determined by sending the voltage generated in the inside to the hardness converter 17 and comparing it with the indentation wedge movement amount versus hardness characteristic value determined in advance for a standard sample of the part to be measured. .

When diagnosing the hardness of a great circle using this diagnostic device, the inner surface of the hole is polished with a polishing tool 20 shown in FIG.

A grinder and a puff can be attached to the tip of the polishing motor 19. First, rough finishing is performed using the grinder 18, and then a puff finishing is performed.

Thereafter, the hardness distribution is measured and recorded in the determiner 21. FIG. 4 shows the state.

When the diagnostic device shown in FIG. 4 is used, the minimum hardness (for example, after use) HV and maximum hardness HVo (before use) of the member to be measured are read, and the change -! jkHV/Hv0 is determined, and if the value exceeds the limit value, a replacement instruction is issued.

These judgments are made by a judge 14 equipped with a simple computer.
Do it with

The diagnostic program used at this time is the 5th rI! As shown in J.

<Effects of the Invention> According to the deterioration diagnosis method of the present invention, maintenance management of members such as stud bolts, which was previously impossible, becomes possible through non-destructive testing.

[Brief explanation of the drawing]

FIG.
FIG. 2 is a cross-sectional view of the essential parts of the device according to the second embodiment of the present invention, showing how it is used; FIG. Figure 3 is a schematic diagram of the TiF grinder inside the hole, Figure 4 is the deterioration diagnosis judger, and Figure 5 is the
The figure shows the diagnostic program of the determiner, Figure 6 (, 1(b) is a side view showing breakage and dangerous parts of the stud bolt, respectively, and Figure 7 shows the heating temperature and time of Cr-Mo-V material for the stud member. Characteristic diagram showing the relationship between initial hardness and initial hardness ratio, No. 8
The figure is a characteristic diagram showing the relationship between heating temperature and time and stress versus initial hardness ratio of Cr-Mo-V material for implantable parts, Fig. 9f
a) (bl is a characteristic diagram showing the relationship between the heating temperature and time versus the initial hardness ratio at the high temperature, low stress position and the high temperature, high stress position (remaining life evaluation position), respectively; Figure 9 IC) is the characteristic diagram showing the relationship between the heating temperature and time versus the initial hardness ratio at the high temperature, low stress position and the high temperature, high stress position (remaining life evaluation position), respectively; Fig. 9 is a characteristic diagram showing the relationship between the remaining life (dl is the Larson-Mira parameter T(c+
Figure 10 shows the degree of cracking of the bolt due to long-term use (temperature T, time t) or the degree of hardness (Vickers hardness) at the relevant location. Characteristic diagram showing, No. 11
Figures (b) and (b) are characteristic diagrams showing changes in hardness in the longitudinal direction of the bolt on the wall surface of the center hole of the bolt. In the drawing, 1... stud bolt, 2... hole, ? -1, 7-2, 7-3, 7-4...Spring, 8-
1.8-2.8-3.8'-4,13・Contactor, 9・・
・Voltmeter, 10.17...Hardness converter, 1..Hydraulic tank, 12..Wedge, 15..Differential transformer, 16..Movable iron plate, 21..Judgment word, 30. Constant current power supply. Patent application person: Kansai Electric Power Co., Ltd. Mitsubishi Heavy Industries, Ltd. (substitute agent)

Claims (3)

[Claims] (1) The amount of change in hardness after use compared to the hardness before use on the inner surface of the hole formed in the member to be measured is determined in advance for the same standard sample as the member to be measured. A deterioration diagnosis method characterized by determining the degree of deterioration of a member to be measured by comparison with a characteristic curve value of hardness. (2) Claim (1) characterized in that the amount of change in hardness of the inner surface of a hole formed in the member to be measured is determined from a change in Vickers hardness or a change in electrical resistance value of the inner surface of the hole. Deterioration diagnosis method described. (3) A contact is attached to the tip of a bar that can be pushed into the inner surface of the hole and is arranged to be able to press the inner surface of the hole, and the amount of push of the wedge that pushes out the contact is determined by the hardness of the inner surface of the hole detected by the contact. In addition to the change in electrical resistance value that corresponds to the hardness of the inner surface of the hole detected by the contactor, the change in the wedge indentation amount or the hardness is determined in advance using a standard sample that is the same as the part to be measured. A deterioration diagnosing device characterized by measuring the degree of deterioration of a member to be measured by comparing the electric resistance value with a characteristic value of magnitude.