JPS5892952A - Estimating method for service life of high temperature member - Google Patents

Abstract

PURPOSE:To provide a method in which an electric or a physical characteristic value of a metallic member used under a high temperature load condition is measured in a non-destructive manner, from the measurements a creep strain damage rate is found on a basis of a relation with the characteristic value, and the member's life is estimated based on a relation between the creep strain damage rate and a creep time damage rate. CONSTITUTION:In a no-load heating test of an unused material such as Cr-Mo-V steels, a relation between hardness and a heating condition parameter P[=T (20+logt)X10<-3>, where T is heating temperature degree R(= degree F + 460), and t is heating time (h)]is shown by a single curve, and a hardness HVN in case a heating takes place for a long period of time under no-load is found by providing a working temperature and a time. In a sample varying a creep damage, a hardness HVN is measured and if a difference DELTAHVC between the hardness HVC and the hardness HVN at a like temperature and time is found, a relation between a creep damage phiCS and the difference is about linear. A hardness HVC1 of a member used at high temperature is then measured, a working condition parameter P1 is computed, from a DELTAHV1 a creep strain damage rate phiCS1 by a strain damage rule is found, from the phiCS1 a creep time damage rate phiCL1 is determined, and a residual life is found by a formula of t2=t1(1/phiCL1-1).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for non-destructively predicting the degree of creep damage of metal material members used at high temperatures.

High-temperature components used in high-temperature equipment such as thermal power, nuclear power, and chemical plants are subjected to external forces at high temperatures, so they may suffer damage or material deterioration during long-term use, and must be replaced at some point (before damage occurs). There is a need to. In order to determine when to replace them, it is necessary to determine the degree of damage over the life of high-temperature components that have been used for long periods of time by some method. Conventionally, this has been done by cutting test pieces directly from parts that have been used for a long time and conducting destructive tests. This conventional method cannot non-destructively measure the degree of lifetime damage, and has disadvantages such as 1) parts must be destroyed, and 2) time-consuming.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method for non-destructively and easily measuring the degree of lifetime damage of metal material members used at high temperatures.

The present invention non-destructively measures electrical or physical characteristic values of metal members used under high-temperature load conditions.

From the measured values, the creep strain damage rate of the member is determined based on the relationship between the known creep strain damage rate [(creep strain)/(creep rupture strain)] and the electrical or physical characteristic value, and A method for predicting the life of a high-temperature member, characterized by determining the life of the member based on the relationship between the known creep strain damage rate and creep time damage rate [(creep time)/(creep rupture time)] from the strain damage rate. .

In particular, the present invention shows that the decrease in hardness of metal material members used at high temperatures increases as the creep damage increases, and this decrease amount ΔH [(Hardness of unloaded heating material H,) - (Hardness of creep-damaged material It has been experimentally clarified that there is a good correlation between the creep strain damage φ6s according to the strain damage law and the present invention has been achieved.

The present invention measures the hardness of metal material members used at high temperatures, and the difference (Hl) between the measured value (Hl) and the hardness Hl in winter when used under no load at the operating temperature and time (known). ΔH
”), the creep strain damage rate φc8 is determined based on the previously known relationship between ΔH and φcIi.

Creep strain damage according to the strain damage law: φcs is determined by the following equation.

4cm ”ε/εf ・・・・・・・・・(1)
The creep time damage rate φCL is determined by the following equation.

φCL"t/'t ・・・・・・・・・(2
) Hereinafter, a method for non-destructively measuring the life of a steam turbine rotor Or-MO-V"m using the method of the present invention at high temperatures will be described in detail.

As a no-load heating test, the unused material of the above-mentioned Cr-MO-V steel was subjected to heat treatment at varying temperatures and times within a heating temperature range of 450 to 600C. Then these 2
The hardness after heating was measured at room temperature. This change in hardness indicates the degree of metallurgical structure change during long-term heating at high temperatures.As shown in Figure 1, the vertical axis represents the hardness, and the horizontal axis represents the heating condition parameter PC=T(20-10gXl0- ", where T: heating temperature' R (='F+460), t: heating time (h
)] as.

When experimental points are plotted, they appear as almost a single curve regardless of heating temperature and time. This curve shows the hardness when heated for a long time without any load.

It can be determined by giving the operating temperature and time.

In addition, a creep test is conducted on the unused Cr-MO-V steel by varying the creep damage rate (temperature, stress, and time) in a temperature range of 500 to 600C.

Next, test the hardness of these test pieces using a hardness tester.
), and the difference between the measured value (H□) and the hardness H, ) when heated at the same temperature and time with no load
, ), and the creep damage (φas
).

As shown in FIG. 2, ΔH□ increases almost linearly with φc11, regardless of the creep test temperature and response.

Next, the creep time damage rate of high-temperature parts in actual machines will be explained. First, measure the hardness H,,1) of the member used at high temperatures, calculate the service condition parameter (P,) from the temperature and time the member was used, and from Figure 1, The hardness H□, ) is determined, and then the difference (ΔH0) between H□ and Hv*1 is determined. From ΔH□, calculate the creep strain damage rate (φcal) according to the strain damage law as shown in Figure 2.

Next, creep damage due to the known 4cm and life damage side (
φCL) based on the relationship diagram (Fig. 3).

The shift leap time damage rate φCL1 is determined from the above φC11l.

The remaining life (11) is determined by the following formula.

(t,: usage time of high temperature parts) The service life of this member until it breaks is t2.

According to the present invention, the degree of creep damage can be predicted non-destructively by measuring the hardness of metal material members used at high temperatures using an echo chip hardness meter, etc. There is no need to perform time-consuming work such as destructive testing.

This has the effect of allowing the remaining life to be easily predicted.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the hardness of the unloaded heating material and heating condition parameters, Figure 2 is a diagram showing the relationship between the amount of hardness reduction due to creep damage and creep damage according to the strain damage law.
Figure 3 shows creep damage due to strain damage law and creep damage due to life damage side.

Claims (1)

[Claims] 1. Nondestructively measure the electrical or physical property values of a metal member used under high-temperature load conditions, and calculate the known creep strain damage rate [(creep strain)/( The creep strain damage rate of the member is determined based on the relationship between the creep rupture strain)] and the electrical or physical property value, and from the creep strain damage rate, the known creep strain damage rate and creep time damage rate [( 1. A method for predicting the lifespan of a high-temperature member, characterized in that the lifespan of the member is determined based on the relationship: creep time)/(creep rupture time). 2. The life of the high-temperature member according to claim 1, wherein the physical characteristic value is the amount of change in hardness [the difference between (the hardness of the unloaded heating material) and (the hardness of the loaded heating material)]. Prediction method.