JPH03221855A - Method for evaluating high temperature damage of welding heat influenced part - Google Patents

Abstract

PURPOSE:To evaluate the degree of high temperature damage by applying a potential difference ratio or the difference of potential differences between an input component and an AC compo nent having the same frequency and phase as that of the input component to a previously formed diagram indicating relation between the potential difference ratio or the difference of potential differences and the degree of high temperature damage. CONSTITUTION:An AC signal having the sine wave of an optional frequency band is generated from an AC oscillator 11 built in a lock-in amplifier 10 and amplified by a power amplifier 12 and the amplified signal is impressed from a current input terminal to a part between a base material part 1a and a welding part 2. Electric signals from potential difference measur ing terminals 5, 6 are respectively amplified by a power amplifier 15 respectively through a signal switching circuit 14 and detected 10 by using a signal from the oscillator 11 as a reference signal, signals other than the electric signal having the same frequency and phase as that of the oscillation signal are removed and the inter-terminal potential difference of only the electric signal having the same frequency and phase as that of the oscillation signal is measured. Then, the potential difference ratio or difference of potential difference between an welding heat influenced part 3 and the base material part 1a is applied to the damage evaluating diagram indicating the relation between the potential difference ratio or the differ ence of potential differences and the degree of high temperature damage, the degree of thigh temperature damage of the influenced part 3 can be evaluated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for evaluating high-temperature damage in a weld heat-affected zone, which is suitable for maintenance management during use of high-temperature equipment having a ferritic heat-resistant steel weld.

[Conventional technology]

Traditionally, the high-temperature damage evaluation method for ferritic heat-resistant steel has been to cut out a part of the heat-resistant steel used as mechanical parts and conduct a destructive test such as a creep test. Methods to do this include inspecting cracks that occur as a result of high-temperature damage using defect inspection methods such as magnetic particle flaw detection and ultrasonic deep flaw detection, and replica methods that examine micro-defects that occurred before cracks have occurred. The method used is to observe and evaluate the degree of high temperature damage.

However, although the method of subjecting it to destructive testing has traditionally been widely used as the most accurate high-temperature damage evaluation method,
It is necessary to cut out the ferritic heat-resistant steel used as mechanical parts for testing, which generally requires large-scale specimen collection and restoration work, and the testing is time-consuming and non-destructive. Establishment of a method to evaluate high-temperature damage quickly and quickly is awaited.

Additionally, non-destructive methods for detecting cracks caused by the accumulation of high'/IA damage are simple, but since cracks often appear only at the end of a structure's lifespan, it is difficult to conduct planned maintenance. In order to manage the damage caused by high temperature before crack initiation,
The establishment of a method to non-destructively evaluate the product is awaited.

Furthermore, a method of evaluating the degree of high-temperature damage by observing micro-defect 9 structural changes before cracks occur using a replica method, etc. has been put into practical use as a method for evaluating high-temperature damage before cracks occur. However, with this method, the inspection target position of the mechanical part is mirror surface r! It is necessary to collect a replica by F-polishing and etching, and then attach this replica to analytical equipment such as a microscope or electron microscope for investigation.Although this is a non-destructive method, it is possible to assess the extent of high-temperature damage at the location to be investigated on the spot. However, it is difficult to evaluate by using the following methods, and there are problems that require time to investigate and evaluate.

[Problem to be solved by the invention]

The present invention was proposed in view of these circumstances, and
High-temperature damage in the welded heat-affected zone of ferritic heat-resistant steel can be easily and accurately evaluated on the spot, and subsequent tests are completely unnecessary. Not only can time and costs be drastically reduced, but also what can be done afterwards? The purpose of the present invention is to provide a high temperature damage evaluation method for weld heat affected zones that enables quick repairs, replacements, etc., and that ultimately improves the reliability of high temperature equipment and reduces operating costs. do.

[Means to solve the problem]

To this end, the present invention provides a method for passing an alternating current through terminals at two points that straddle the weld heat affected zone of ferritic heat-resistant steel, and to and base material 2
A damage evaluation line that shows the relationship between a potential difference ratio or a potential difference created in advance by measuring each potential difference between points and the potential difference ratio or potential difference of an alternating current component with the same frequency and phase as the human component and the degree of high temperature damage. The feature is that the degree of high temperature damage in the weld heat affected zone is evaluated by applying it to the diagram.

[Effect]

In the method of the present invention, the degree of high-temperature damage in the weld heat-affected zone of ferritic heat-resistant steel can be determined by simply arranging and connecting six terminals, two terminals for current input and four terminals for potential difference output, on the outer surface of the target position. Therefore, compared to destructive testing methods that require sample collection and repair work, and non-destructive testing methods that require polishing, etching, and replica collection of the survey target location, the investigation is simpler and easier to conduct than samples. Lifespan evaluation can be performed on the spot without the need for long-term destructive tests or tissue investigation tests after collection.

Furthermore, measurement is performed using an alternating current method instead of a direct current method in which noise current cannot be removed, and highly accurate life evaluation is possible without measurement errors caused by noise current.

Furthermore, high-temperature damage is evaluated not by the absolute value of the electrical resistance value of the weld heat-affected zone, where significant accumulation of high-temperature damage is observed, but by the ratio or difference between the N product of high-temperature damage and the electrical resistance value of the base material, where the N product is slight. It is possible to eliminate the influence of variations in measured values due to temperature, etc., making it possible to perform highly accurate life evaluations.

〔Example〕

The method for evaluating high-temperature damage of a weld heat-affected zone according to the present invention is
To explain one embodiment of the welded part of a heat-resistant ferritic steel pipe using drawings, Fig. 1 is a front view of a heat-resistant ferritic steel pipe with measurement terminals arranged, and Fig. 2 is a detailed cross-sectional view of the part shown in Fig. 1. , FIG. 3 is a system diagram of the potential difference measuring circuit, and FIG. 4 is an explanatory diagram of a specific experimental example.

First, before explaining the embodiments, the process and principle of the method of the present invention will be explained.

The method of the present invention focuses on the potential difference method by examining a method for evaluating high-temperature damage before crack initiation that is easier than the conventional replica method. The potentiometric method has already been put into practical use as a method to non-destructively detect the depth of surface cracks.
This method involves passing a constant current between two points across the crack,
Measure the potential difference between two points across the crack on the line segment connecting the same two points, and take advantage of the fact that the deeper the crack, the greater the potential difference between the two points including the crack. Evaluation is performed using a crack depth evaluation reference diagram that shows the relationship between the potential difference measured with a crack of known depth and the crack depth. In this case, the absolute value of the potential difference between two points across the forged part is evaluated. Terminal contact condition.

It is not possible to effectively detect potential difference changes due to micropores, coarse precipitates, etc. before crack initiation because they are affected by the temperature of the measurement position.

Therefore, in the present invention, focusing on the fact that most of the creep damage in ferritic heat-resistant steel is located in the weld heat-affected zone, current input is applied between two points that straddle the weld heat-affected zone. Measure the potential difference between two points that straddle the weld heat affected zone on the line connecting the two points, that is, the damaged area, and simultaneously measure the potential difference of the base material, that is, the undamaged area on the same line, and calculate the potential difference between the two points. Measure the ratio of or the difference between the two potentials.

Furthermore, when the potential difference side of an actual structural component is constant, a large amount of noise current flows, and without removing the noise, it is difficult to detect a slight change in potential due to damage before a crack occurs.

Therefore, in the method of the present invention, the applied current is an AC sinusoidal current, and the current waveform between the terminals for potential difference detection is detected in synchronization with the AC waveform of the input current, and current components other than the input waveform are detected. In other words, the potential difference of only the current waveform with the noise current component removed is measured.

The method of the present invention based on such a principle will be described below to evaluate high-temperature damage in welded parts of Ferai I series heat-resistant steel pipes that are used as parts of high-temperature equipment.

First, in FIG. 1, the arrangement of measurement terminals in the base metal part 1a, the welded part 2, and the welded heat affected zone 3 of the ferritic heat-resistant steel pipe 1 is as follows. A pair of potential difference measurement terminals 5, 5, which are placed at the weld zone 2 and which measures the weld heat affected zone 3, which is the damaged area, are connected to the line segment connecting the terminals 4.4. A pair of potential difference measuring terminals 6 arranged in the upper welding part 2 and the welding heat affected zone 3 and further measuring the base material 91t 1 a which is an undamaged part,
6 is also the base material part la on the line segment connecting the terminals 4, 4.
Place it in

As shown in FIG. 2, each of these terminals 4, 5.6 has a diameter of 1.9 mm and a depth of 0.9 mm, which are provided in each arrangement member.
Insert the platinum wire 8 of 0.5 mm into the 5 mm mounting hole 7 from Spora 1 to
It is formed by welding and filling the periphery with a ceramic-based insulating adhesive 9 to prevent oxidation.

Therefore, an alternating current is applied from these two terminals 4.4, and the other 4
When measuring the potential difference between two points in each pair terminal arrangement using terminals 5.5 and 6.6, in FIG. Generates an alternating current signal, increasing power 11"
Increased by the device 12 rp l,, current human power αR1i child 4,
4 to the base metal part la and the welding part 2 in FIG. At this time, in order to maintain a constant current, a reference resistor 13 that is sufficiently larger than the application target section described in "2" is connected to the input circuit.

Thus, the potential difference measuring terminals 5, 5 and the potential difference measuring terminal 6.
The electrical signals from AC oscillator 11 are amplified by power multipliers 15 through signal switching circuits 14, respectively, and detected in lock-in amplifier 10 using the signal from AC oscillator 11 as a reference signal, which is the same as the oscillation signal. Electric signals other than those having the same frequency and phase are removed, and the potential difference between the terminals of only signals having the same frequency and phase as the oscillation signal is measured.

Next, the potential difference ratio or the potential difference between the potential difference of the welding heat affected zone 3 and the potential difference of the base metal part 1a obtained by this measurement is used as a damage evaluation that shows the relationship between the potential difference ratio or the potential difference and the degree of high-temperature damage created in advance. When applied to the diagram, welding heat affected zone 3
The extent of high-temperature damage is revealed.

0 Next, a specific experimental example will be explained with reference to FIG.

2% Cr-IM as shown within the chain line in the figure.

A notched creep rupture test piece 1b with a notch 3b' formed in the weld heat affected zone 3b of a steel welded joint was tested at 600°C x 8kg.
f 7m2. A creep rupture test was conducted under the conditions of 55 Q° C.

The results are shown in the diagram in the same figure.

In the figure, the horizontal axis is the creep rupture life consumption rate shown in equation (1), and the vertical axis is the potential difference ratio of the weld heat affected zone to the base metal normalized by the initial value shown in equation (2).

Interruption time creep rupture life consumption rate - rupture time...(1) Potential difference of base metal part during potential difference test of weld heat affected zone during potential difference ratio test normalized to initial value. Potential difference of base metal part before test. ...(2) As shown in Figure 4, the potential difference ratio of the weld heat-affected zone to the normalized base metal is 30% of the creep rupture life consumption rate.
It can be seen that the earth is monotonically added to the creep rupture life consumption rate, and that the life consumption rate from the middle of life to the end of life can be easily and accurately evaluated by the method of the present invention.

〔Effect of the invention〕

In short, according to the present invention, alternating current is applied to terminals at two points that straddle the weld heat affected zone of ferritic heat-resistant steel, and between the two points that straddle the weld heat affected zone on the line segment connecting the two points and the base material. Measure each potential difference between two points, and calculate the potential difference ratio of the AC component with the same frequency and phase as the input component, or the potential difference of 4°, to determine the relationship between the potential difference ratio or potential difference difference and the degree of high temperature damage. By applying the damage evaluation diagram shown in the diagram to evaluate the degree of high-temperature damage in the weld heat-affected zone, it is possible to easily and accurately evaluate the high-temperature damage in the weld heat-affected zone of ferritic heat-resistant steel on the spot. There is no need for subsequent testing, and therefore, the time and cost required for in-service inspections of high-temperature equipment made of ferritic heat-resistant steel can be greatly reduced, and subsequent repairs and replacements can be carried out quickly. INDUSTRIAL APPLICABILITY The present invention is extremely useful industrially because it provides a high-temperature damage evaluation method for a weld heat-affected zone that can improve the reliability of high-temperature equipment and reduce operating costs.

[Brief explanation of drawings]

FIG. 1 is a front view of a Ferri I heat-resistant steel pipe with measurement terminals arranged in an embodiment in which the high-temperature damage evaluation method of a weld heat-affected zone of the present invention is applied to welding heat of a ferritic heat-resistant steel pipe;
FIG. 2 is a detailed cross-sectional view of the part (■) in FIG. 31, FIG. 3 is a system diagram of the potential difference measuring circuit, and FIG. 4 is an explanatory diagram of a specific experimental example. 1... Ferritic heat-resistant steel pipe, 1a... Base metal part, 2
... Welding heat, 3... Welding heat affected zone, 4... Current input terminal, 5... Potential difference measurement terminal, 6... Potential difference measurement terminal, 7... Mounting hole, 8... Platinum wire, 9... Insulating adhesive, lO... Ronfin amplifier, 11... AC oscillator, 12... Power multiplier, 13... Reference resistor,
14... Signal switching circuit, 15... Electric power converter.

Claims (1)

[Claims] An alternating current is passed through two terminals that straddle the weld heat affected zone of ferritic heat-resistant steel, and each potential difference between the two points that straddle the weld heat affected zone on the line segment connecting the two points and between two points of the base metal is calculated. By measuring the potential difference ratio or potential difference of an AC component with the same frequency and phase as the input component, and applying it to a damage evaluation diagram showing the relationship between the potential difference ratio or potential difference difference and the high temperature damage degree, created in advance, A method for evaluating high-temperature damage to a weld heat-affected zone, the method comprising evaluating the degree of high-temperature damage to the weld heat-affected zone.