JPS59100858A - Method for measuring remaining service life of metallic material - Google Patents

Abstract

PURPOSE:To measure nondestructively a remaining service life of a material by comparing a deviation value obtained by comparing an eddy current value from a test piece prior to usage with an eddy current of a material used actually with characteristics between a fracture surface transition temp. and an eddy current of the metallic material. CONSTITUTION:The variation of the eddy current value (shown as an ECT value in the following) is raised with rise of a fracture surface transition temp. Thus, service hours of the metallic material, i.e. the relationship between the variations of the fracture surface transition temp. and the ECT are measured previously, and a probe coil is brought into contact successively with each part of a measuring material 4 to read the ECT value and to allow the read value to correspond to a graph, and the fact that how much service service life is dissipated is measured. Thereby, the remaining service life up to the service limit hour can be measured nondestructively from this result.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for measuring the remaining life of a metal material that allows non-destructive measurement of the remaining life of a metal material used under high temperature and high pressure.

[Technical background of the invention and its problems]

Metal materials used in prime movers, such as steam turbines, are used under high temperatures and pressures for long periods of time.
From the standpoint of preventing accidents, it is necessary to detect in advance the decline in financial strength as the usage time passes.

Conventionally, as a method for determining the remaining life Thff1ll of metal materials, it was common practice to take out a part of the material used as a test piece and perform a destructive test on this test piece to measure the remaining life of the material. . However, with this method, taking out the test piece from the rotating shaft or blade, for example, causes problems such as performance deterioration and unbalance, which poses difficult problems in practice.

For this reason, conventionally, the temperature during steam turbine operation.

Simulated data obtained based on pressure was compared with values measured while the steam turbine was stopped, and based on the comparison values, financial decline was determined empirically and parts were replaced.

However, this method requires skill, which can lead to erroneous judgments about financial decline, such as trying to replace parts even though they don't actually have to be replaced, or replacing parts even though they should be replaced. The inaccuracies such as not being used were a problem, and it was not desirable from the standpoint of energy saving these days.

[Purpose of the invention]

In view of the above points, the present invention focuses on the fact that there is a proportional relationship between the financial decline value of metal materials and the eddy current value, and non-destructively estimates the remaining life of the metal material by measuring changes in the eddy current value. The present invention provides a method for measuring the remaining life of metal materials.

[Summary of the invention]

The present invention compares the eddy current value from the test piece before use with the eddy current value of the material actually used, and the deviation value is determined from the characteristics of the metal material's fracture surface transition temperature and overcurrent value. It is characterized by determining the lifetime consumption of materials by comparing the

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

In general, when metal materials, especially low-alloy steel, are used under high-temperature, high-pressure steam, impurities segregate at the grain boundaries of the material, as shown in Figure 1, and this results in poor toughness. decreases, the fracture surface transition temperature (hereinafter referred to as FATT) increases significantly, and a phenomenon of embrittlement of the material occurs. It is generally well known that this embrittlement phenomenon accelerates the progress of the creep phenomenon and leads to material failure.

In this way, the fracture phenomenon and the embrittlement phenomenon of a material are integrally linked, and if this embrittlement phenomenon can be produced non-destructively over time, the remaining life of a metal material can be measured. Eddy current flaw detection is a method for measuring the embrittlement phenomenon of metal materials.

In other words, in the eddy current flaw detection method, when a current is passed through a probe coil through the metal material to be measured, an eddy current is generated in the metal material, and the amount of change in the impedance of the probe coil that changes due to the influence is called the eddy current value (hereinafter referred to as ECT). By measuring the amount of change in impedance, the state of the metal material, expressed as the amount of eddy current, can be determined. FIG. 2 shows, as an example, ICr-IM, which is often used as a turbine rotor.

This shows the changes in the fracture surface transition temperature and ECT value of lv steel.The change in ECT value clearly indicates the behavior of the material during use, as shown in Figure 1, and increases as the fracture surface transition temperature rises. That is clear. In this way, the relationship between the usage time of the metal material, that is, the fracture surface transition temperature, and the change in the ECT value is determined in advance, and a small test piece of the metal material or other material to be measured before use is used as the reference test piece. However, if this is not available, use a small test piece that has undergone the same initial heat treatment as the reference test piece, or use a material of the same type as the material to be measured. As shown in Fig. 3, a part of the test piece whose temperature is sufficiently low and which does not receive much stress is used as an unused standard test piece.
The probe coil 2 is brought into contact with the eddy current measuring device 3 to adjust the ECT indication to zero, and then the probe coil 2 is brought into contact with each part of the material to be measured 4 in sequence, and the ECT value is read, as shown in FIG. Corresponding to the graph, it is possible to measure how much time the device has actually been used at the time of measurement, in other words, how much life has been consumed, and from this result, it is possible to measure the remaining life until the usage limit time.

〔Effect of the invention〕

As explained above, according to the present invention, by measuring the ECT value of a metal material, it is possible to determine how much life the metal material consumes and how much life it has left until its usage limit.
Since it is possible to economize non-destructively and accurately, it has a remarkable effect on improving the reliability of equipment and effectively using resources.

[Brief explanation of drawings]

Figure 1 shows the aging behavior of metal materials used under high temperature and high stress conditions. Figure 2 shows the changes in fracture surface transition temperature (FATT) and eddy current (direct) in a deterioration test using the eddy current flaw detection method. 1 and 3 are schematic diagrams showing embodiments of the present invention. 1.-Reference test piece 2 Probe coil 3 Eddy current measuring device 4 Material to be measured (7317) Agent Patent attorney rule Kensuke Chika (and 1 others) Figure 1 Figure 2 FACT〈6c) Figure 3

Claims (1)

[Claims] Compare the eddy current value obtained from the test piece before use with the eddy current value of the metal material used in the base under high temperature and high pressure, and if a deviation occurs, calculate the deviation value in advance. A method for measuring the remaining life of a metal material in which the consumption amount over the life of the metal material is measured by comparing characteristic values from the fracture surface transition temperature and eddy current value of the metal material.