JP2003315251A - High temperature damage evaluating method for heat- resisting steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high temperature damage evaluating method for heat- resisting steel performing high temperature damage evaluation to a heat-resisting steel (annealed martensitic stainless steel). <P>SOLUTION: High temperature evaluation (remaining service life evaluation) is performed (a void number density method) by preparing a creep void evaluating chart to express the relation between the number density of creep voids and a service life ratio on the annealing martensitic stainless steel from a multi- axis stress test in advance, and determining the number density of the creep voids of a part exposed to a multiaxial stress field from a void observing means to determine the service life ratio of the part based on this number density of the creep voids and the creep void evaluating chart. Also, the part exposed to the multiaxial stress field, where hardness measurement is difficult, is evaluated with this void number density method, and the high temperature evaluating method (the remaining service life evaluation) of the whole high temperature apparatus is performed by evaluating a part, where hardness measurement is easy, with the hardness measurement. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature damage evaluation method for heat resistant steel, and is useful when applied to the evaluation of the remaining life of high temperature equipment made of tempered martensitic steel.

[0002]

2. Description of the Related Art The creep damage evaluation method for heat-resistant steels (low alloy steels, tempered martensitic steels, etc.) that have been used in high temperature equipment has been used to evaluate the creep damage on the grain boundaries generated in the creep process at the damaged parts. A-parameter method to evaluate tee,
A metallographic method for estimating creep damage from the distribution of precipitates and morphological changes, a miniature creep test piece is taken from the site of use, and a creep test is actually conducted at arbitrary stress and temperature to estimate the remaining life. There is a destructive test method.

[0003]

Of the above-mentioned conventional techniques,
The A-parameter method cannot be applied to tempered martensitic steel because creep cavities do not occur in the uniaxial creep test. The metallographic method is applied only to the weld heat-affected zone that breaks brittlely, and cannot be applied to tempered martensitic steel that breaks ductilely. The destructive test method requires a long time for the test, and the amount of material collected from high-temperature equipment is large, so that the applicable site is very limited. Especially for steam turbine rotors and main valves,
It is difficult to collect a test piece from a site with severe creep damage.

Therefore, in view of the above circumstances, it is an object of the present invention to provide a high temperature damage evaluation method for heat-resistant steel, which enables high temperature damage evaluation for tempered martensitic steel.

[0005]

[Means for Solving the Problems] First to solve the above problems
The high temperature damage evaluation method of the heat resistant steel of the invention is 9 to 12% by weight C
It is a high temperature damage evaluation method for tempered martensitic steel, which is r steel, and a creep void evaluation diagram showing the relationship between creep void number density and life ratio for tempered martensitic steel is created in advance by a multiaxial stress test. What to do,
By the void observing means, the creep void number density of the portion exposed to the multiaxial stress field is obtained, and by obtaining the life ratio of the portion based on this creep void number density and the creep void evaluation diagram, The feature is that the remaining life is evaluated.

A method for evaluating high temperature damage of heat resistant steel of the second invention
The method is a tempered martenser which is 9-12 wt% Cr steel.
It is a high temperature damage evaluation method for iron steel, and it is difficult to measure hardness.
For the part exposed to the multiaxial stress field,
Residual life is evaluated by the high temperature damage evaluation method for heat resistant steel,
For parts where hardness is easy to measure, the usage time t and the damaged part
Using the operating temperature T of G, the value G of the G parameter₁Calculate
The effect of aging only G₁The value of
And the hardness Hv of the stress-free part₁Of the simple aging material
G-Hv / Hv₀From the diagram, G₁Hv corresponding to₁/ H
v₀Initial hardness Hv₀Or
Initial hardness Hv₀In advance, the hardness Hv of the damaged part
₂To measure Hv₂/ Hv₀Calculated, and
The relationship between hardness and G parameter
Hardness ratio Hv / Hv obtained by organizing₀And the G’parameter
From one master curve showing the relationship, the Hv₂/ H
v₀Value of the G'parameter corresponding to the value of₂To calculate
That this G₂G which we asked earlier₁By subtracting
The value of the softening acceleration ΔG due only to
And the value of ΔG in the master curve formula
Estimating the stress based on the estimated stress σ and
Based on the working temperature T and the creep rupture diagram, the rupture time t
_rAnd the breaking time t_rAnd life time t
It is characterized by seeking.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view showing a schematic procedure of a high temperature damage evaluation method for heat-resistant steel according to an embodiment of the present invention, FIG. 2 and FIG.
Is a diagram showing an example of a portion to be evaluated by the high temperature damage evaluation method, FIG. 4 is a creep void evaluation diagram showing the relationship between creep void number density and life ratio, and FIGS. 5, 6 and 7 are multiaxial stress tests. It is explanatory drawing which shows the example of a method. Also, FIG.
Is a diagram showing the relationship between the G parameter and the hardness ratio, and FIG. 9 is G ′.
The figure which shows the relationship (master curve) between a parameter and hardness ratio, FIG. 10 is a figure which shows the procedure of a hardness method, and FIG. 11 is a figure which shows the relationship between stress and fracture time.

As shown in FIG. 1, in the high temperature damage evaluation method of the present embodiment, 9 to 12 used for a turbine rotor, a main valve, etc. by a void number density method and a hardness method.
High temperature damage evaluation (remaining life evaluation) of tempered martensitic steel which is a wt% Cr steel is performed.

[0010] Tempered martensitic steel, which is a heat-resistant steel, is softened during high temperature use, and further softened under stress. From this, even in tempered martensitic steel, the Larson mirror type temperature / time / stress parameter G'is arranged into one curve (master curve) irrespective of temperature and stress (see FIG. 9, details will be described later). ), It was found that high temperature damage evaluation is possible. Based on this knowledge, high temperature damage evaluation (remaining life evaluation) is performed by the hardness method for a portion whose hardness can be easily measured, such as the central hole 2 of the rotating shaft 1 of the turbine rotor as shown in FIG.

On the other hand, high temperature equipment such as a turbine rotor has a complicated shape and often has a cutout portion, and it is difficult to measure hardness at the cutout bottom which is expected to be the most damaged portion. Therefore, it has been found that the notch bottom is generally exposed to a multiaxial stress field, and creep voids occur even in tempered martensitic steel under such a multiaxial stress. Based on this knowledge, for the parts where hardness measurement is difficult,
High temperature damage evaluation (remaining life evaluation) by the void number density method
I do. For example, the mounting portion 5 of the rotor blade 3 of the turbine rotor as shown in FIG. 3 is notched, and it is difficult to measure the hardness of the groove portion (notch bottom) 4, but the number of voids in such a portion is small. High temperature damage is evaluated by the density method.

As will be described later in detail, as shown in FIG. 1, in the void number density method, the void number of the blade groove portion 4 is observed to obtain the creep void number density (S1), and the creep void number density is shown in FIG. The residual life is evaluated based on the creep void evaluation diagram shown (S2), and the hardness of the rotor center hole 2 is measured by the hardness method (S3). This hardness and the master curve (G 'shown in FIG. The remaining life is evaluated based on the relationship between the parameter and the hardness ratio) (S4). Thus, the high temperature damage evaluation (remaining life evaluation) of the entire high temperature equipment (turbine rotor) can be performed.

Here, the void number density method and the hardness method will be described in detail with reference to FIGS.

<Void Number Density Method> A tempered martensitic steel was previously subjected to a multiaxial stress test to find the creep void number density as shown in FIG. 4 and the ratio of the breaking time _tr to the operating time (operating time) t. A creep void evaluation diagram showing the relationship with a certain life ratio t / t _r is created. As shown in the figure, creep voids increase with time under multiaxial stress.

Next, the creep void number density is obtained by using a general replica method as the void observation means. That is, a replica is taken from the blade groove portion 4 which is a high temperature damage evaluation portion (the unevenness of the object surface is transferred to a thin film), the replica is observed by SEM (Scanning Electron Microscopy), and the number of creep voids is measured. Divide by the observation area to obtain the creep void number density (pieces / mm ² ). Then, this creep void number density and FIG.
Based on the creep void evaluation diagram of FIG. 4, the remaining life is evaluated by determining the life ratio t / t _r of the blade groove portion 4 as illustrated by the dotted line in FIG.

As described above, according to the present void number density method, the creep void evaluation diagram is used to obtain a high accuracy for the portion of the tempered martensitic steel exposed to the multiaxial stress field. High temperature damage evaluation (remaining life evaluation) can be performed.

The multi-axial stress test is carried out, for example, in Patent No. 300.
It can be carried out by utilizing a multiaxial stress test method as disclosed in Japanese Patent No. 9621. The outline of this multiaxial stress test method will be described with reference to FIGS.

As shown in FIG. 5, the cylindrical test piece 11 used in this test method is mainly composed of a cylindrical portion 15, a connecting portion 14 and a test portion 13. That is, the cylindrical test piece 1
1, one end surface 12 side of the cylindrical portion 15 is closed and formed by a projecting curved surface composed of a smooth connecting portion 14 and a test portion 13,
The thickness of the protruding curved surface gradually increases as the distance from the central axis portion increases,
The shape is smoothly continuous with the wall thickness of the cylindrical portion 15. Here, while the cylindrical portion 15 has a cylindrical shape,
The test portion 13 and the connecting portion 14 have a substantially spherical shell shape. In particular, the test portion 13 projects as a part of a thin spherical shell having a uniform thickness t and having the same center as the cylindrical portion 15 at the cylindrical central axis portion of the protruding curved surface as shown in FIG. 6, for example. The uniform thickness t of the test portion 13 is the wall thickness measured in the direction in which the internal pressure acts. In addition, the uniform thickness t
The area of the test portion 13 having the can be arbitrarily increased depending on the design of the cylindrical test piece 11.

The connecting portion 14 has, for example, an outer surface curved so that the outer peripheral surface of the test portion 13 is smoothly connected to the outer peripheral surface of the cylindrical portion 15 as shown in FIG. The inner surface is curved so that the thickness gradually increases toward 15. Since the internal pressure is applied to the connecting portion 14 as well as the test portion 13, changes in thickness and curvature are minimized so that a peculiar stress portion is not formed as much as possible.

In such a cylindrical test piece 11, since the outer peripheral surface of the test portion 13 is spherical and thin, the stress in the thickness direction is zero when an internal pressure is applied, and it is 2 at a right angle to the thickness direction.
Axial tensile stress equal to the direction, that is, equal biaxial tensile stress will be received. Therefore, the thickness of the test part 13 is t
(Mm), an average radius as r _m (mm), the internal pressure p (M
Upon receiving Pa), as shown in the following equation, equal stresses σ _t and σ θ are generated in two directions at right angles. Therefore, if the test portion 13, the connecting portion 14, and the like are properly designed as described above, equilibrium biaxial tensile stress test becomes possible. σ = σ _t = σ θ = pr _m / t

Here, if the test portion 13 has a true spherical shape,
Theoretically, the stress in the thickness direction is zero, and the "equal biaxial tensile stress test" is possible in which the axial tensile stress is equal in two directions perpendicular to the thickness direction. However, in reality, it is difficult to process it into a true spherical shape, so it may be processed to the extent that it can be recognized as a thin spherical shell by a normal processing method. Even with such a shape, "biaxial tensile stress It is possible to carry out a "test". Furthermore, an elliptical shape close to a sphere,
It is considered that a test similar to the "biaxial tensile stress test" can be performed even with the quadric surface shape. As shown in FIG. 8, the shape from the connecting portion 14 to the test portion 13 is most preferably a state in which two spheres having different radii are in contact with the center. Test section 3
Is almost close to the point, and the test piece is easy to make, but the measurement is difficult.

The above-mentioned cylindrical test piece 11 can be applied to the creep test by maintaining a predetermined test temperature and atmosphere in a heating means such as a high temperature furnace 21 as shown in FIG. That is, as shown in FIG. 5, a high-temperature furnace 21 is installed in the internal pressure creep tester 25, a cylindrical test piece 11 is inserted into the high-temperature furnace 21, and a pump 23 is connected to the pipe 18 by a pipe 18 in the cylindrical test piece 11. The cylindrical test piece 11 is connected via the internal pressure of the water 20.

Specifically, the other end 17 of the cylindrical portion 15 is closed by a nozzle 28 and welded 19, and a pipe 18 is connected to the nozzle 28. Water 20 is passed through the pipe 18 to carry out a cylindrical test. The pressure is transmitted to the piece 15 to apply the internal pressure. The internal pressure is adjusted by the pump 23. The internal pressure creep tester 25 itself can use the one conventionally used. The high temperature furnace 21 is a container for maintaining the cylindrical test piece 11 at a predetermined test temperature and atmosphere, and a window 22 is provided in a part thereof.
The window 22 is provided with a measuring means 24 such as a telescope, and the displacement of the tip 16 of the test portion 13 of the cylindrical test piece 11 can be observed. Specifically, in order to focus the telescope on the tip 16 of the test section 13, the telescope is moved and the amount of movement is measured as the displacement of the tip 16. Alternatively, the displacement is obtained by fixing the measuring means 24 such as a laser range finder outside the window 22 and reading the distance to the tip 16 of the test section 13.

The above is the outline of the multiaxial stress test method. When the creep void number density is obtained by using such a multiaxial stress test method, an equal biaxial multiaxial stress field is generated by applying a predetermined internal pressure to the cylindrical test piece 11 under a predetermined temperature condition. After the rupture and at every predetermined time until the rupture, a replica of the surface of the test portion 13 of the cylindrical test piece 11 is sampled, the replica is observed by SEM, and the number of creep voids is measured. Divide by the observed area to obtain the creep void number density.

<Hardness Method> In the hardness method, the evaluation diagram of FIG. 9 obtained by arranging the experimental data as shown in FIG. 8 (the relationship between the G ′ parameter and the hardness ratio Hv / Hv ₀ is shown). The high temperature damage evaluation (remaining life evaluation) is performed according to the procedure shown in FIG.

The experimental data shown in FIG. 8 is obtained as follows. That is, in order to produce a simple aging material of tempered martensitic steel, the temperature is 500 to 600 ° C. and the time is 1000.
Perform a long-term heating test of -60,000 hours. Further, in order to determine the hardness change during creep deformation (particularly in the accelerated creep region), a creep test under the conditions of temperature 650 ° C.-stress 8,10 kg / mm ² and temperature 600 ° C.-stress 10, 14, 20 kg / mm ^2. Then, an intermediate test piece and a fracture test piece of tempered martensitic steel are produced. Then, the hardness Hv of the simple aging material and the creep damage imparting material (intermediate test piece, fracture test piece) is measured,
The relationship between the hardness for the simple aging material and the creep damage imparting material as shown in FIG. 8 and the G parameter, which is the logarithm of the Larson mirror parameter, is obtained. The formula for the G parameter is: G = log [(T + 273) (25 + log t)] (1)

In FIG. 8, the hardness measurement value Hv is standardized by the initial hardness Hv ₀ . As shown in FIG. 8, the decrease in hardness is a state where no stress is applied (no-load heating state).
However, it occurs remarkably when the G parameter exceeds 4.4 (curve shown by a solid line in FIG. 8). Further, in the stress-loaded state of 8 kg / mm ² or more, the greater the stress, the more the hardness decreases.

Next, the decrease in hardness is separated into the effect G due to only aging and the softening acceleration (ΔG) due to the stress σ, and the G'parameter represented by the sum of the two: G '= G + ΔG and the experimental data of FIG. To organize. It is assumed from FIG. 8 that the effect of softening acceleration ΔG due to stress appears at 80 MPa or more. G '=
G + ΔG = log [(T + 273) (25 + log t)] + ΔG (2) Here, when σ ≦ 80 MPa, ΔG = 0, when σ ≧ 80 MPa, ΔG = 0.00022 (σ−80)

FIG. 9 shows the relationship between the hardness ratio Hv / Hv ₀ and the G'parameter. As shown in the figure, all the data can be represented by one master curve by arranging by G'parameter. Therefore, using this master curve, the remaining life is evaluated in the procedure shown in FIG.

As shown in FIG. 10, the operating time (use time) t and the use temperature T of the damaged portion are used as known data (S11). That is, when the damaged portion is the rotor center hole 2, the operating time t of the turbine rotor and the operating temperature T of the rotor center hole 2 are used as known data. Then, first, the hardness Hv ₁ of the stress-unloaded portion such as the shaft end of the turbine rotor, that is, the unloaded heating portion that is heated but is hardly loaded with stress is measured (S12). Next, from the operating time t of the known data and the operating temperature T, the value G _{1 of the} G parameter is calculated by using the above-mentioned effect G only by the aging equation G: log = ((T + 273) (25 + log t)]. (S13). That is, this G ₁ is a value that represents the effect of aging alone.

Further, G-Hv / Hv of the simple aging material shown in FIG.
_{The value of} the hardness ratio Hv ₁ / Hv ₀ corresponding to G ₁ is obtained from the ₀ diagram (curve shown by the solid line in FIG. 8) (S14), and the value of this hardness ratio Hv ₁ / Hv ₀ The initial hardness Hv ₀ is calculated from the hardness Hv ₁ measured in step S15 (S15). In addition,
This process of obtaining the initial hardness Hv ₀ is used when the initial hardness cannot be measured as in an existing steam turbine, for example, and the initial hardness can be measured as in a newly installed steam turbine. For these, the initial hardness may be measured in advance.

Subsequently, the hardness Hv ₂ of the damaged portion is measured (S16). Then, the hardness ratio Hv ₂ / Hv ₀ is calculated from this Hv ₂ and the previously obtained Hv ₀ (S17), and FIG.
From the master curve of 0 (G'-Hv / Hv ₀ diagram),
The value G ₂ of the G ′ parameter corresponding to Hv ₂ / Hv ₀ is calculated (S18). Next, by subtracting the previously obtained G ₁ from this G ₂ (G ₂ −G ₁ ), the softening acceleration ΔG due to only the stress is obtained, and the value of this ΔG and the equation (2) expressing the master curve are obtained. Expression of ΔG in: ΔG = 0.00022
The stress σ is estimated (calculated) based on (σ−80) (S19).

Finally, the estimated stress σ and known data are used.
Creep rupture as shown in FIG. 11 based on the working temperature T
Diagram (stress σ generally obtained by experiments and breakage
Interval t _rFrom the line diagram showing the relationship with_rThe value of
Obtained (S20), this breaking time t_rAnd driving known data
The remaining life is calculated from the time t (t_r-T). Hiding
Therefore, the remaining life can be evaluated by the hardness method. Na
The creep void fracture diagram in Fig. 11 shows the operating temperature t₁, t
₂, t₃It is a curve for each, but this is Larson Mira
-General creep in a single curve using parameters
A broken line diagram may be used.

As described above, according to the present hardness method, for the temperable martensitic steel where hardness can be measured, the G'parameter and the hardness ratio Hv /
By using one master curve representing the relationship with Hv ₀ , highly accurate high temperature damage evaluation (remaining life evaluation) can be performed.

The high-temperature damage evaluation method (void number density method and hardness method) of the present invention is not limited to turbine rotors and main valves, but is used for various high-temperature equipment such as other high-temperature rotating bodies and boilers. It can be applied to high temperature damage evaluation of tempered martensitic steel.

[0036]

As described above in detail with the embodiments of the invention, the high temperature damage evaluation method for heat-resistant steel of the first invention is performed at a high temperature of tempered martensitic steel which is 9 to 12% by weight Cr steel. A damage evaluation method, in which a multi-axial stress test is performed in advance to create a creep void evaluation diagram showing the relationship between the creep void number density and the life ratio for tempered martensitic steel, and the multi-axial stress is evaluated by the void observation means. The remaining life is evaluated by obtaining the creep void number density of the part exposed to the field and obtaining the life ratio of the part based on this creep void number density and the creep void evaluation diagram. And

Therefore, according to the high temperature damage evaluation method for heat-resistant steel of the first invention, the creep void evaluation diagram is used for the portion of the tempered martensitic steel exposed to the multiaxial stress field. Highly accurate high temperature damage evaluation (remaining life evaluation) can be performed.

A method for evaluating high temperature damage of heat resistant steel of the second invention
The method is a tempered martenser which is 9-12 wt% Cr steel.
It is a high temperature damage evaluation method for iron steel, and it is difficult to measure hardness.
For the part exposed to the multiaxial stress field,
Residual life is evaluated by the high temperature damage evaluation method for heat resistant steel,
For parts where hardness is easy to measure, the usage time t and the damaged part
Using the operating temperature T of G, the value G of the G parameter₁Calculate
The effect of aging only G₁The value of
And the hardness Hv of the stress-free part₁Of the simple aging material
G-Hv / Hv₀From the diagram, G₁Hv corresponding to₁/ H
v₀Initial hardness Hv₀Or
Initial hardness Hv₀In advance, the hardness Hv of the damaged part
₂To measure Hv₂/ Hv₀Calculated, and
The relationship between hardness and G parameter
Hardness ratio Hv / Hv obtained by organizing₀And the G’parameter
From one master curve showing the relationship, the Hv₂/ H
v₀Value of the G'parameter corresponding to the value of₂To calculate
That this G₂G which we asked earlier₁By subtracting
The value of the softening acceleration ΔG due only to
And the value of ΔG in the master curve formula
Estimating the stress based on the estimated stress σ and
Based on the working temperature T and the creep rupture diagram, the rupture time t
_rAnd the remaining life from the breaking time tr and the operating time t
It is characterized by seeking.

Therefore, according to the high-temperature damage evaluation method for heat-resistant steel of the second aspect of the present invention, a portion which is difficult to measure hardness and is exposed to a multiaxial stress field and a portion which is easy to measure hardness are respectively High temperature equipment (turbine rotor, main valve, etc.) by evaluating by the method (void number density method and hardness method)
The high temperature damage evaluation (remaining life evaluation) of the whole can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a schematic procedure of a high temperature damage evaluation method for heat resistant steel according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a portion evaluated by the high temperature damage evaluation method.

FIG. 3 is a diagram showing an example of a portion evaluated by the high temperature damage evaluation method.

FIG. 4 is a creep void evaluation diagram showing the relationship between the number density of creep voids and the life ratio.

FIG. 5 is an explanatory diagram showing an example of a multiaxial stress test method.

FIG. 6 is an explanatory diagram showing an example of a multiaxial stress test method.

FIG. 7 is an explanatory diagram showing an example of a multiaxial stress test method.

FIG. 8 is a diagram showing a relationship between a G parameter and a hardness ratio.

FIG. 9 is a diagram showing a relationship (master curve) between a G ′ parameter and a hardness ratio.

FIG. 10 is a diagram showing a procedure of a hardness method.

FIG. 11 is a diagram showing the relationship between stress and rupture time.

[Explanation of symbols]

1 Rotor axis of turbine rotor 2 Rotor center hole 3 Turbine rotor blades 4 blade groove 5 Blade mounting part 11 Cylindrical test piece 12 end faces 13 Testing Department 14 Connection 15 Cylindrical part 16 tip 17 other end 18 piping 19 welding 20 water 21 high temperature furnace 22 windows 24 measuring instruments 23 pumps 25 Internal pressure creep tester 28 nozzles

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G050 AA01 BA10 BA12 CA04 DA02                       EA01 EA04 EB07 EC05                 2G055 AA03 AA12 BA11 EA08 FA01                       FA02

Claims (2)

[Claims] 1. A high-temperature damage evaluation method for tempered martensitic steel, which is a 9-12 wt% Cr steel, wherein a creep void number density and a life ratio of the tempered martensitic steel are preliminarily tested by a multiaxial stress test. Creating a creep void evaluation diagram that represents the relationship, by the void observation means, obtain the creep void number density of the part exposed to the multiaxial stress field, and this creep void number density, and the creep void evaluation diagram A high temperature damage evaluation method for heat resistant steel, characterized in that the remaining life is evaluated by determining the life ratio of the above-mentioned parts based on the above. 2. A tempered steel which is 9-12 wt% Cr steel.
A method for evaluating high temperature damage of rutensitic steel, For parts that are difficult to measure hardness and are exposed to a multiaxial stress field
According to the method for evaluating high temperature damage of heat resistant steel according to claim 1.
To evaluate the remaining life, For areas where hardness measurement is easy, Using the operating time t and the operating temperature T of the damaged part, G parameter
Value G₁The effect of aging alone by calculating
G₁To find the value of Hardness Hv of stress-free part₁Is measured, and the simple aging material G-
Hv / Hv₀From the diagram, G₁Hv corresponding to₁/ Hv₀
Initial hardness Hv₀Or the initial
Hardness Hv₀In advance, Hardness of damaged part Hv₂To measure Hv₂/ Hv₀Calculate
However, hardness and G for simple aging materials and creep damage imparting materials
Hardness ratio Hv / Hv obtained by arranging parameter relationships₀
Is a single master curve that represents the relationship between
Hv₂/ Hv₀G'parameter corresponding to the value of
The value of G₂To calculate, This G₂G which we asked earlier₁Stress by subtracting
The value of the softening acceleration ΔG is calculated by
And the formula of ΔG in the formula of the master curve
And estimating the stress, This estimated stress σ and operating temperature T, and the creep rupture diagram
Based on the fracture time t _rAnd the breaking time t_rAnd messenger
Heat-resistant steel characterized by finding the remaining life from the operating time t
High temperature damage evaluation method.