WO2015059815A1 - Method for predicting creep residual life of product degraded by heat and pressure, and method for creating calibration curve used in the prediction method - Google Patents

Method for predicting creep residual life of product degraded by heat and pressure, and method for creating calibration curve used in the prediction method Download PDF

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Publication number
WO2015059815A1
WO2015059815A1 PCT/JP2013/078957 JP2013078957W WO2015059815A1 WO 2015059815 A1 WO2015059815 A1 WO 2015059815A1 JP 2013078957 W JP2013078957 W JP 2013078957W WO 2015059815 A1 WO2015059815 A1 WO 2015059815A1
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product
evaluation range
crack
calibration curve
length
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PCT/JP2013/078957
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French (fr)
Japanese (ja)
Inventor
荒川　大輔
西田　秀高
栄郎 松村
啓司 森下
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中国電力株式会社
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Priority to PCT/JP2013/078957 priority Critical patent/WO2015059815A1/en
Priority to JP2015512418A priority patent/JP5859710B2/en
Publication of WO2015059815A1 publication Critical patent/WO2015059815A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/20—Metals
    • G01N33/204—Structure thereof, e.g. crystal structure
    • G01N33/2045—Defects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/006—Crack, flaws, fracture or rupture
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0071—Creep
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/0202—Control of the test
    • G01N2203/0212—Theories, calculations
    • G01N2203/0218—Calculations based on experimental data

Definitions

  • the present invention relates to a method for predicting the remaining creep life of a product deteriorated by heating and pressurization, and a calibration curve creating method used for this prediction method.
  • An object of the present invention is to provide a method for predicting the creep remaining life of a product deteriorated by heating and pressurization, and a calibration curve creating method used for this prediction method.
  • the method for creating a calibration curve used in the method for predicting the remaining creep life of the first product deteriorated by heating and pressurization according to the present invention can be arbitrarily evaluated on the surface of the second product deteriorated by heating and pressurization. Including a step of setting a range and a step of determining whether or not a crack has occurred within the evaluation range.
  • the method of creating a calibration curve used in the method for predicting the remaining creep life of the first product deteriorated by heating and pressurization according to the present invention is arbitrary on the surface of the second product deteriorated by heating and pressurization. And a step of determining whether or not a crack has occurred within the evaluation range, and if there is no crack within the evaluation range, the void is within the evaluation range.
  • a step of obtaining a number density, and a step of creating a calibration curve representing a relationship between the number density of the obtained void and the damage rate of the second product When cracks are generated within the evaluation range, the step of obtaining the number of crystal grains over which the maximum crack generated within the evaluation range spans, and the relationship between the number of crystal grains obtained and the damage rate of the second product And a step of creating a calibration curve representing the first product and the second product may have a bainite structure.
  • the evaluation range it is preferable to set the evaluation range to a location where cracks are likely to occur on the surface of the second product.
  • the maximum crack is cut, if the length of each cut portion is less than a predetermined ratio with respect to the longer length of the two adjacent cracks, the maximum crack is It is preferable to calculate the maximum crack length or the number of crystal grains over which the maximum cracks are considered, assuming that they are not broken. More preferably, the predetermined ratio is half.
  • the first product and the second product are preferably hollow tubes, and may be, for example, boiler piping having a bent portion.
  • the pressurization is preferably an internal pressure.
  • the second product at least two types of products heated at different temperatures and pressurized at different pressures were used, and the number density of voids and the maximum cracks required for each of these at least two types of products were used.
  • a calibration curve may be created based on the length and / or the number of grains that the maximum crack spans. In this case, it is preferable that the lifetimes of at least two types of products are different within 25% of the lifetimes of other products based on the lifetime of the longest product.
  • the method for predicting the remaining creep life of a product deteriorated by heating and pressurization includes a step of setting an arbitrary evaluation range on the surface of the product, and whether or not a crack has occurred within the evaluation range. And determining the number of voids within the evaluation range and determining the product damage rate from the obtained number density of voids. And further comprising a process, In the evaluation range, when a crack has occurred, the method further includes a step of determining the length of the maximum crack generated in the evaluation range, and a step of determining a product damage rate from the obtained maximum crack length, The product is characterized by having a bainite structure.
  • a step of setting an arbitrary evaluation range on the surface of the product and whether cracks are generated within the evaluation range If there is no crack in the evaluation range, the step of obtaining the number density of voids in the evaluation range and the product damage rate from the obtained number density of voids And a process for obtaining In the evaluation range, if a crack has occurred, a step of obtaining the number of crystal grains spanned by the maximum crack generated in the evaluation range and a step of obtaining a product damage rate from the number of obtained crystal grains.
  • the product may have a bainite structure.
  • the evaluation range it is preferable to set the evaluation range to a location where cracks are likely to occur on the product surface.
  • the maximum crack is cut, if the length of each cut portion is less than a predetermined ratio with respect to the longer length of the two adjacent cracks, the maximum crack is It is preferable to calculate the maximum crack length or the number of crystal grains over which the maximum cracks are considered, assuming that they are not broken. More preferably, the predetermined ratio is half.
  • the product is preferably a hollow tube, for example, a boiler pipe having a bent portion.
  • the pressurization is preferably performed by applying an internal pressure to the product.
  • the present invention it is possible to provide a method for predicting the remaining creep life of a product deteriorated by heating and pressurization, and a calibration curve creating method used for this prediction method.
  • FIG. 6 is a graph showing the relationship between the maximum crack length and the sample damage rate when (a) the damage rate is 0 to 1.0 and (b) the damage rate is 0.7 to 1.0 in an embodiment. is there. It is a graph which shows the relationship between the extended M parameter and the damage rate of a sample in one Embodiment.
  • the number density of voids within the evaluation range And a step of creating a calibration curve representing the relationship between the number density of the obtained voids and the damage rate of the second product, If a crack has occurred within the evaluation range, a step for obtaining the length of the maximum crack generated within the evaluation range and a calibration curve representing the relationship between the obtained maximum crack length and the damage rate of the second product
  • the first product and the second product have a bainite structure.
  • the first product and the second product are made of a material having a bainite structure and causing creep deformation by heating and pressing.
  • An example of such a material is cast steel, but is not limited thereto.
  • the first product and the second product are preferably made of the same material.
  • the shape of the first product and the second product is not particularly limited, and can be, for example, a hollow tube, a plate, or a rod, but is preferably a hollow tube.
  • the cross-section of the hollow tube may be any shape, for example, circular, oval, or polygonal, but with a corner if the strength of the hollow tube is taken into account. It is preferably not circular or elliptical, more preferably circular.
  • a boiler pipe having a bent portion As such a hollow tube, for example, a boiler pipe having a bent portion can be cited.
  • boiler piping has been considered to have a ferrite structure or a pearlite structure, and thus the creep remaining life has been predicted according to a method for predicting the creep remaining life of a product having a ferrite structure or pearlite structure.
  • the present inventors have found that the bent portion changes to have a bainite structure with slow cooling when the bent portion of the boiler piping is created. Therefore, if the creep remaining life of a boiler pipe having a bent portion is predicted using the calibration curve created by the calibration curve creating method according to the present invention, the creep remaining life of the boiler pipe can be accurately predicted. It becomes possible.
  • the shape of the first product and the shape of the second product may be the same or different, but are preferably the same or similar, and more preferably the same.
  • the first product and the second product are products deteriorated by being placed under conditions of a constant high temperature and a constant pressure higher than normal pressure, respectively.
  • the temperature range is not particularly limited as long as each product has a bainite structure.
  • the range may be 210 ° C. to 550 ° C., and preferably 350 ° C. to 550 ° C.
  • the heating temperature of the first product and the heating temperature of the second product may be the same or different, but are preferably the same.
  • the pressure range is not particularly limited as long as it is higher than normal pressure (0.1 MPa), but may be, for example, 0.2 MPa to 1000 MPa, preferably 0.3 MPa to 500 MPa, and preferably 0.5 MPa to 300 MPa.
  • the pressure applied to the first product and the pressure applied to the second product may be the same or different, but are preferably the same.
  • the method of applying pressure to the product is not particularly limited, and external pressure may be applied or internal pressure may be applied. However, when each product is a hollow tube, it is preferable to apply the internal pressure. When applying an internal pressure to the second product, it is preferable to deteriorate the second product by an internal pressure creep test.
  • the internal pressure creep test is a method of measuring the lifetime of a hollow tube by applying an internal pressure to the hollow tube in a high-temperature furnace and creeping the hollow tube as necessary.
  • the internal pressure creep test can be performed on the hollow tube itself, including the effects of altered layers such as oxides on the outer surface and inner surface of the hollow tube, which occurs when the hollow tube is used as boiler piping, for example. It is excellent in that it can be tested. Further, since the stress due to the internal pressure is applied to the hollow tube in the same manner as when actually used in the boiler, it is possible to accurately measure the life of the boiler piping.
  • the evaluation range can be set by selecting an arbitrary portion having an arbitrary width on the surface of the second product. Although wide is arbitrary, for example, it may be in the range of 0.3mm 2 ⁇ 1.0mm 2. Moreover, although a selection location is arbitrary, it is preferable that it is a location where a crack is likely to occur on the surface of the second product, and those skilled in the art can obtain such location from empirical rules and calculations. According to the calibration curve creation method according to the present invention, even if the evaluation range is arbitrarily set, the calibration curve with very little error depending on the setting method is applied by applying the maximum crack length to the product having a bainite structure. The advantageous effect that can be created. Therefore, if the calibration curve created in this way is used, the remaining creep life of the first product deteriorated by heating and pressurization can be accurately predicted.
  • the method for determining whether or not a crack has occurred within the set evaluation range is not particularly limited, and a known method can be used.
  • the structure is observed with a scanning electron microscope (SEM). You may judge by.
  • a calibration curve is created by paying attention to voids generated on the surface of the second product.
  • the method for obtaining the number density of voids within the evaluation range is not particularly limited, and a known method can be used. For example, after obtaining the number of voids within the evaluation range, the number of voids obtained is evaluated within the evaluation range. It can be obtained by dividing by the area. This may be obtained, for example, by performing tissue observation using a scanning electron microscope.
  • the damage rate of a product is a ratio representing how much time has passed under the same heating condition and the same pressurizing condition as determining the lifetime with respect to the lifetime of the product.
  • the product life is the time required for the product to break by constant heating and constant pressure.
  • the lifetime of a product can be determined by known methods, for example, by measuring a product of the same structure made from the same material as the product by constant heating and pressurization until it actually breaks.
  • the heating condition and the pressurizing condition for predicting the remaining lifetime may be any one of the conditions.
  • the maximum crack means a crack having the longest length among cracks generated in a product due to deterioration due to heating and pressurization within an evaluation range.
  • the crack is cut, if the length of the cut portion is equal to or less than a predetermined ratio with respect to the longer length of the two adjacent cracks, both the cracks and It is preferable to determine the length of the crack by regarding the broken portion as a single connected crack.
  • the present inventors in the case where the crack is broken in the middle, whether or not the broken portion will be a crack in the future is stronger from the longer of the two cracks adjacent to this broken portion Found to be affected.
  • the predetermined ratio is preferably half, more preferably 40%, and still more preferably 30%.
  • the length of the crack is the length of the straight line connecting the ends of the crack, and the length of the part that is cut is the two parts that the cut part and the two cracks adjacent to the cut part create.
  • a method of obtaining the length of the crack will be specifically described with reference to FIG.
  • cracks 10 (indicated by thick lines in FIG. 1) are generated along the plurality of crystal grains 1.
  • the length 3 of the cut portion is less than half of the longer length 4 of the two cracks adjacent to the cut portion.
  • the length of the crack 10 is determined to be the crack length 2.
  • the method for measuring the length of the crack is not particularly limited, and a known method can be used.
  • the crack length may be measured by observing the structure of the surface of the product with a scanning electron microscope.
  • a method for creating a calibration curve used in the method for predicting the remaining creep life of the first product deteriorated by heating and pressurization Including a step of setting an arbitrary evaluation range on the surface of the second product deteriorated by heating and pressurization, and a step of determining whether or not a crack is generated within the evaluation range.
  • the step of obtaining the number density of voids and the step of creating a calibration curve representing the relationship between the number density of the obtained voids and the damage rate of the second product are further included.
  • the step of obtaining the number of crystal grains over which the maximum crack generated within the evaluation range spans, and the relationship between the number of crystal grains obtained and the damage rate of the second product
  • a step of creating a calibration curve representing the first product and the second product may have a bainite structure. That is, in the above-described method, instead of obtaining the maximum crack length, the number of crystal grains spanning the maximum crack is obtained, and further, instead of creating a calibration curve representing the relationship between the maximum crack length and the damage rate of the second product. A calibration curve representing the relationship between the number of crystal grains over which the maximum crack extends and the damage rate of the second product is created.
  • the number of crystal grains over which a crack extends refers to the number of crystal grain boundary faces or sides where cracks run.
  • a predetermined ratio with respect to the longer length of the two adjacent cracks, both the cracks and It is preferable to determine the number of crystal grains over which the crack extends, assuming that the broken portion is one connected crack.
  • the predetermined ratio is preferably half, more preferably 40%, and still more preferably 30%.
  • cracks 10 are generated along the plurality of crystal grains 1. Although the crack 10 is cut off in the middle, the length 3 of the cut portion is less than half of the longer length 4 of the two cracks adjacent to the cut portion. Regarded as a single crack, including broken parts. As a result, the number of crystal grains over which the crack 10 extends is determined to be 6.
  • the method for measuring the number of crystal grains over which cracks cross is not particularly limited, and a known method can be used.
  • the number of crystal grains may be measured by observing the structure of the surface of the product with a scanning electron microscope. .
  • the calibration curve creation method according to the present invention in predicting the remaining life of a product having a bainite structure, even if the evaluation range is arbitrarily set by applying the number of crystal grains over which the maximum crack extends, it is set. This produces an advantageous effect that a calibration curve with very little error depending on the method can be created.
  • the first product when no crack is generated in the first product is obtained. It can be a calibration curve for predicting the remaining creep life of the product.
  • only one type of product may be used as the second product, or at least two types of products heated at different temperatures and pressurized at different pressures may be used.
  • the void number density, the maximum crack length, and / or the number of crystal grains spanning the maximum crack are appropriately determined, and all the obtained void number densities, the maximum crack length,
  • a calibration curve is created by determining the relationship with the damage rate of the second product using the number of grains over which the maximum crack spans.
  • the lifetimes of these products are comparable.
  • the same level means that the life of two or more types of products is preferably a difference of 25% or less, more preferably a difference of 20% or less, based on the life of the longest product. More preferably, the difference is within 10%.
  • a person skilled in the art can appropriately set the temperature and pressure applied to each product so that two or more types of products have the same life. For example, in Example 1 and Example 3 of the present application, two types of products, that is, a product heated at 550 ° C. and pressurized at 145 MPa and a product heated at 525 ° C. and pressurized at 240 MPa are used, which are common to these.
  • the approximate curve shown in FIG. 9 was obtained as a calibration curve representing the relationship between the void number density and the damage rate of the second product.
  • the approximate curve shown in FIG. 16 is obtained as a calibration curve representing the relationship between the maximum crack length and the damage rate of the second product
  • the approximate curve shown in FIG. 17 is obtained from the number of crystal grains spanning the maximum crack and the second product. It was obtained as a calibration curve representing the relationship with the damage rate.
  • the following is performed. First, an arbitrary evaluation range is set on the surface of the first product. Next, it is determined whether or not a crack has occurred within this evaluation range. If no crack has occurred, the remaining creep life is predicted based on the voids present on the surface of the first product. That is, first, the number density of voids within the evaluation range is obtained, and the obtained damage number density is obtained by substituting the obtained number density of voids into the void number density of the calibration curve prepared by the above-described method. Can do.
  • the remaining life of the first product can be predicted to be 1.5 times the time of heating and pressurization so far. Further, if a crack is generated within the evaluation range, the remaining creep life is predicted based on the maximum crack length generated on the surface of the first product. That is, first, the length of the maximum crack generated in the first product within the evaluation range is obtained. Then, by inserting the obtained maximum crack length into the maximum crack length of the calibration curve created by the above-described method, the damage rate of the corresponding product can be obtained. For example, if the corresponding damage rate is determined to be 0.80, the remaining life of the first product can be predicted to be 25% of the time of heating and pressurization so far.
  • the method for predicting the remaining creep life of a product deteriorated by heating and pressurization is as follows: When a crack is generated within the evaluation range, the length of the maximum crack generated within the evaluation range is determined. Instead of “obtaining the step of determining the damage rate of the product from the obtained maximum crack length” and “determining the number of crystal grains over which the maximum crack generated within the evaluation range spans” And a step of obtaining a damage rate of the product from the number of crystal grains ”.
  • the following is performed. First, the number of crystal grains over which the maximum crack generated in the first product extends is obtained. Next, the number of crystal grains obtained is inserted into the number of crystal grains across the maximum crack in the calibration curve created by the above-described method. Thereby, the damage rate of the corresponding product can be obtained.
  • Example 1 An internal pressure creep test was carried out using a cylindrical tube (STPA 22, outer diameter ⁇ 56.5 mm, inner diameter 47.5 mm, length 35.0 mm) made of chromium molybdenum steel and having a bainite structure as a sample.
  • One sample was subjected to an internal pressure of 145 MPa at a temperature of 550 ° C. (Test 1), and another sample was subjected to an internal pressure of 240 MPa at a temperature of 525 ° C. (Test 2).
  • the life of the sample in Test 1 and the life of the sample in Test 2 were about the same as the life of the sample in Test 2, which was about 23% shorter than that of the sample in Test 1.
  • the damage rates were 0, 0.12, 0.19, 0.26, 0.50, and 0.70, and for test 2, the damage rates were 0.00, 0,.
  • the structure of the sample was observed using a scanning electron microscope (SEM). Specifically, for each sample, an arbitrary evaluation range having a width of 1.0 mm 2 is determined, and the structure is observed at magnifications of 100 times, 500 times, and 1000 times, and the number of voids is determined. Examined. In order to show that a large error does not occur depending on how the evaluation range is selected, an evaluation range having a width of 0.3 mm 2 is further set from the evaluation range having a width of 1.0 mm 2 . The structure was also observed in this small evaluation range, and the number of voids was examined.
  • FIG. 9 shows the relationship between the average number of voids and the damage rate obtained from all SEM results. In all SEM results, no cracks occurred.
  • Example 2 the remaining creep life of a cylindrical tube having a bainite structure was predicted using FIG. 9 created in Example 1.
  • a pipe made of chromium molybdenum steel STPA 22, JIS standard G 3457 “arc welded carbon steel pipe for piping” was bent while being heated slowly so that it could be used in a boiler of a thermal power plant.
  • STPA 22 chromium molybdenum steel
  • JIS standard G 3457 arc welded carbon steel pipe for piping
  • the structure of the bent portion of the piping was observed using SEM.
  • SEM SEM image
  • the void number density was determined from the SEM image and found to be 50. From FIG. 9 created in Example 1, since the damage rate when the void number density is 50 is found to be 0.41, it is predicted that the damage rate of the bent portion of the boiler piping is 0.41. I was able to. In other words, it was possible to predict that the remaining life of the bent portion of this pipe was about 2.5 times the usage time up to now.
  • Example 3 An internal pressure creep test using a cylindrical tube (STPA 22, outer diameter ⁇ 56.5 mm, inner diameter 47.5 mm, length 35.0 mm) having a bainite structure made of chromium molybdenum steel material under the same conditions as in Example 1 Went.
  • One sample was subjected to an internal pressure of 145 MPa at a temperature of 550 ° C. (Test 1), and another sample was subjected to an internal pressure of 240 MPa at a temperature of 525 ° C. (Test 2).
  • the life of the sample in Test 1 and the life of the sample in Test 2 were about the same as the life of the sample in Test 2, which was about 23% shorter than that of the sample in Test 1.
  • test 1 when the damage rate is 0, 0.11, 0.18, 0.25, 0.47, 0.66, 0.76, 0.85 and 1.00, and for test 2 Observed the structure of the sample when the damage rate was 0.00, 0.14, 0.23, 0.32, 0.61, 0.85, 0.98, and 1.00.
  • the position of the evaluation range was set so as to include a central portion in the length direction of the pipe, which is likely to cause cracks in the cylindrical pipe.
  • the setting of the area of the evaluation range is determined as if the crack extends over 1.0 mm 2 or more areas comprises the entire crack, the size of 0.3 mm 2 or 1.0 mm 2 in other cases Set to have.
  • the structure is observed with a scanning electron microscope (SEM) at magnifications of 10 times, 50 times, 100 times, and 400 times, and the number of voids present in the evaluation range and cracks are present.
  • SEM scanning electron microscope
  • extended M parameter the maximum crack length and the number of crystal grains over which the maximum crack crosses
  • FIG. 10 (b) the maximum crack when the damage rate in Test 1 is 0.76 is cut off in the middle, but the length of the cut-off portion is the length of both adjacent cracks.
  • the maximum crack length was determined to be 518 ⁇ m, and the extended M parameter was determined to be 6.
  • the maximum crack when the damage rate in Test 1 is 0.85 is cut off at a plurality of locations, but the length of each cut-off location is Since each of the adjacent cracks was less than half of the length of the longer crack, the crack and the cut portion were regarded as one connected crack, and the maximum crack length was 1.09 mm.
  • the extended M parameter was determined to be 14.
  • Test 1 is summarized in Table 2
  • Test 2 is summarized in Table 3.
  • FIG. 16 shows a graph representing the relationship between the maximum crack length and the damage rate created based on Tables 2 and 3
  • FIG. 17 shows a graph representing the relationship between the extended M parameter and the damage rate.
  • Example 4 In Example 4, the remaining creep life of a cylindrical tube having a bainite structure was predicted using FIGS. 16 and 17 created in Example 3.
  • STPA 22 chromium molybdenum steel
  • JIS standard G 3457 arc welded carbon steel pipe for piping
  • the bent part of the pipe was observed with a SEM.
  • the maximum crack length was determined from the SEM image, and the result was 1.7 mm. From FIG. 16 created in Example 1, since the damage rate when the maximum crack length is 1.7 mm is found to be 0.95, the damage rate of the bent portion of the boiler piping is 0.95. I was able to predict. That is, the remaining life of the bent portion of the pipe could be predicted to be about 5% of the usage time up to now.

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Abstract

[Problem] To provide a method for predicting creep residual life of products degraded due to heat and pressure. Specifically, there is provided a method for predicting creep residual life, characterized in that the method includes a step for establishing a discretionary evaluation range on the surface of a product, and a step for determining whether or not cracking has occurred within the evaluation range, and further includes a step in which, in the event that no cracking has occurred within the evaluation range, a void number density within the evaluation range is calculated, and a step in which a damage rate of the product is calculated from the void number density, the method further including a step in which, in the event that cracking has occurred within the evaluation range, the number of crystal grains that are cut across by the largest crack occurring within the evaluation range is calculated, and a step in which a damage rate of the product is calculated from the number of crystal grains obtained thereby, the product having a bainite structure.

Description

加熱及び加圧により劣化した製品のクリープ余寿命の予測方法、及び、この予測方法に用いる検量線作成方法Prediction method for creep remaining life of product deteriorated by heating and pressurization, and calibration curve creation method used for this prediction method
　本発明は、加熱及び加圧により劣化した製品のクリープ余寿命の予測方法、及び、この予測方法に用いる検量線作成方法に関する。 The present invention relates to a method for predicting the remaining creep life of a product deteriorated by heating and pressurization, and a calibration curve creating method used for this prediction method.
　火力発電設備や原子力発電設備等において用いられる機械部品は、長期間に渡って高温・高圧条件におかれることから、徐々に塑性変形を起こし、クリープ寿命に達すると破断してしまう。従って、火力発電設備や原子力発電設備を安全かつ経済的に運転するためには、用いられている機械部品のクリープ余寿命を的確に予測することによって、最適な時期に機械部品の交換を行うことが求められる。 Mechanical parts used in thermal power generation facilities, nuclear power generation facilities, etc. are subjected to high temperature and high pressure conditions for a long period of time, so that they gradually undergo plastic deformation and break when the creep life is reached. Therefore, in order to operate thermal power generation facilities and nuclear power generation facilities safely and economically, the machine parts must be replaced at the optimal time by accurately predicting the remaining creep life of the machine parts used. Is required.
　このような機械部品に使用されている耐熱鋼のクリープ余寿命を予測する方法としては、例えば特開昭６３－２３５８６１号公報が示すように、実際に稼動している火力発電設備や原子力発電設備の機械部品の耐熱鋼から試験片を切り出して、クリープ破断試験を行い、その破断時間から余寿命を予測する方法が知られているが、この方法では、実際に稼動している設備から試験片を切り出して長時間に渡って試験をする必要があり、煩雑である。
　この他、目視検査、及び、レプリカ法によるクリープボイドを検出する方法などが知られており、例えば、クリープボイドを検出する方法の一種として、最大ボイド粒界占有率（Ｍパラメータ）を使用する方法が、例えば国際公報ＷＯ０２／０１４８３５号公報により報告されている。 As a method for predicting the remaining creep life of heat-resistant steel used in such mechanical parts, for example, as disclosed in Japanese Patent Laid-Open No. 63-235861, a thermal power generation facility and a nuclear power generation facility that are actually in operation A method is known in which a test piece is cut out from a heat-resistant steel of a machine part, a creep rupture test is performed, and the remaining life is predicted from the rupture time. It is necessary to carry out a test over a long period of time, and it is complicated.
In addition, visual inspection and a method of detecting a creep void by a replica method are known. For example, a method of using the maximum void boundary occupancy (M parameter) as a kind of a method of detecting a creep void. Is reported, for example, in International Publication WO02 / 014835.
　本発明は、加熱及び加圧により劣化した製品のクリープ余寿命の予測方法、及び、この予測方法に用いる検量線作成方法を提供することを目的とする。 An object of the present invention is to provide a method for predicting the creep remaining life of a product deteriorated by heating and pressurization, and a calibration curve creating method used for this prediction method.
　本発明に係る、加熱及び加圧により劣化した第１製品のクリープ余寿命を予測する方法に用いる検量線を作成する方法は、加熱及び加圧により劣化した第２製品の表面において、任意の評価範囲を設定する工程と、評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、評価範囲内において、亀裂が生じていない場合には、評価範囲内において、ボイドの個数密度を求める工程と、得られたボイド個数密度と第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、
　評価範囲内において、亀裂が生じている場合には、評価範囲内において生じた最大亀裂の長さを求める工程と、得られた最大亀裂長さと第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、第１製品および第２製品がベイナイト組織を有することを特徴とする。 The method for creating a calibration curve used in the method for predicting the remaining creep life of the first product deteriorated by heating and pressurization according to the present invention can be arbitrarily evaluated on the surface of the second product deteriorated by heating and pressurization. Including a step of setting a range and a step of determining whether or not a crack has occurred within the evaluation range. If no crack has occurred within the evaluation range, the number density of voids within the evaluation range And a step of creating a calibration curve representing the relationship between the obtained void number density and the damage rate of the second product,
If a crack has occurred within the evaluation range, a step for obtaining the length of the maximum crack generated within the evaluation range and a calibration curve representing the relationship between the obtained maximum crack length and the damage rate of the second product And the first product and the second product have a bainite structure.
　また、本発明に係る、加熱及び加圧により劣化した第１製品のクリープ余寿命を予測する方法に用いる検量線を作成する方法は、加熱及び加圧により劣化した第２製品の表面において、任意の評価範囲を設定する工程と、評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、評価範囲内において、亀裂が生じていない場合には、評価範囲内において、ボイドの個数密度を求める工程と、得られたボイドの個数密度と第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、
　評価範囲内において、亀裂が生じている場合には、評価範囲内において生じた最大亀裂がまたがる結晶粒の数を求める工程と、得られた結晶粒の数と第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、第１製品および第２製品がベイナイト組織を有することを特徴としても良い。 In addition, the method of creating a calibration curve used in the method for predicting the remaining creep life of the first product deteriorated by heating and pressurization according to the present invention is arbitrary on the surface of the second product deteriorated by heating and pressurization. And a step of determining whether or not a crack has occurred within the evaluation range, and if there is no crack within the evaluation range, the void is within the evaluation range. A step of obtaining a number density, and a step of creating a calibration curve representing a relationship between the number density of the obtained void and the damage rate of the second product,
When cracks are generated within the evaluation range, the step of obtaining the number of crystal grains over which the maximum crack generated within the evaluation range spans, and the relationship between the number of crystal grains obtained and the damage rate of the second product And a step of creating a calibration curve representing the first product and the second product may have a bainite structure.
　評価範囲を、第２製品の表面において亀裂が生じやすい箇所に設定することが好ましい。 It is preferable to set the evaluation range to a location where cracks are likely to occur on the surface of the second product.
　最大亀裂が寸断されている場合に、寸断されている各箇所の長さが、その寸断箇所が隣接する両亀裂のうち長い方の長さに対して所定の割合以下であれば、最大亀裂は寸断されていないものとみなして、最大亀裂長さ、または、最大亀裂がまたがる結晶粒の数を求めることが好ましい。所定の割合が半分であることがより好ましい。 When the maximum crack is cut, if the length of each cut portion is less than a predetermined ratio with respect to the longer length of the two adjacent cracks, the maximum crack is It is preferable to calculate the maximum crack length or the number of crystal grains over which the maximum cracks are considered, assuming that they are not broken. More preferably, the predetermined ratio is half.
　第１製品および第２製品が中空管であることが好ましく、例えば、曲がり部分を有するボイラ用配管であっても良い。これらの場合に、加圧は内圧であることが好ましい。 The first product and the second product are preferably hollow tubes, and may be, for example, boiler piping having a bent portion. In these cases, the pressurization is preferably an internal pressure.
　第２製品として、互いに異なる温度で加熱され、かつ、互いに異なる圧力で加圧された少なくとも２種類の製品を用い、これら少なくとも２種類の製品のそれぞれについて求められた、ボイドの個数密度、最大亀裂長さ、および／または、最大亀裂がまたがる結晶粒の数に基づいて、検量線を作成しても良い。この場合、少なくとも２種類の製品の寿命が、最も長い製品の寿命を基準として他の製品の寿命が２５％以内の差であることが好ましい。 As the second product, at least two types of products heated at different temperatures and pressurized at different pressures were used, and the number density of voids and the maximum cracks required for each of these at least two types of products were used. A calibration curve may be created based on the length and / or the number of grains that the maximum crack spans. In this case, it is preferable that the lifetimes of at least two types of products are different within 25% of the lifetimes of other products based on the lifetime of the longest product.
　本発明に係る、加熱及び加圧により劣化した製品のクリープ余寿命を予測する方法は、製品の表面において、任意の評価範囲を設定する工程と、評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、評価範囲内において、亀裂が生じていない場合には、評価範囲内において、ボイドの個数密度を求める工程と、得られたボイドの個数密度から製品の損傷率を求める工程とをさらに含み、
　評価範囲内において、亀裂が生じている場合には、評価範囲内において生じた最大亀裂の長さを求める工程と、得られた最大亀裂長さから製品の損傷率を求める工程とをさらに含み、製品がベイナイト組織を有することを特徴とする。 According to the present invention, the method for predicting the remaining creep life of a product deteriorated by heating and pressurization includes a step of setting an arbitrary evaluation range on the surface of the product, and whether or not a crack has occurred within the evaluation range. And determining the number of voids within the evaluation range and determining the product damage rate from the obtained number density of voids. And further comprising a process,
In the evaluation range, when a crack has occurred, the method further includes a step of determining the length of the maximum crack generated in the evaluation range, and a step of determining a product damage rate from the obtained maximum crack length, The product is characterized by having a bainite structure.
　また、本発明に係る、加熱及び加圧により劣化した製品のクリープ余寿命を予測する方法は、製品の表面において、任意の評価範囲を設定する工程と、評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、評価範囲内において、亀裂が生じていない場合には、評価範囲内において、ボイドの個数密度を求める工程と、得られたボイドの個数密度から製品の損傷率を求める工程とをさらに含み、
　評価範囲内において、亀裂が生じている場合には、評価範囲内において生じた最大亀裂がまたがる結晶粒の数を求める工程と、得られた結晶粒の数から製品の損傷率を求める工程とをさらに含み、製品がベイナイト組織を有することを特徴としても良い。 Further, according to the method of predicting the creep remaining life of a product deteriorated by heating and pressurization according to the present invention, a step of setting an arbitrary evaluation range on the surface of the product and whether cracks are generated within the evaluation range. If there is no crack in the evaluation range, the step of obtaining the number density of voids in the evaluation range and the product damage rate from the obtained number density of voids And a process for obtaining
In the evaluation range, if a crack has occurred, a step of obtaining the number of crystal grains spanned by the maximum crack generated in the evaluation range and a step of obtaining a product damage rate from the number of obtained crystal grains. Further, the product may have a bainite structure.
　評価範囲を、製品の表面において亀裂が生じやすい箇所に設定することが好ましい。 It is preferable to set the evaluation range to a location where cracks are likely to occur on the product surface.
　最大亀裂が寸断されている場合に、寸断されている各箇所の長さが、その寸断箇所が隣接する両亀裂のうち長い方の長さに対して所定の割合以下であれば、最大亀裂は寸断されていないものとみなして、最大亀裂長さ、または、最大亀裂がまたがる結晶粒の数を求めることが好ましい。所定の割合が半分であることがより好ましい。 When the maximum crack is cut, if the length of each cut portion is less than a predetermined ratio with respect to the longer length of the two adjacent cracks, the maximum crack is It is preferable to calculate the maximum crack length or the number of crystal grains over which the maximum cracks are considered, assuming that they are not broken. More preferably, the predetermined ratio is half.
　製品が中空管であることが好ましく、例えば、曲がり部分を有するボイラ用配管であっても良い。これらの場合に、加圧は製品に内圧を加えることにより行われるのが好ましい。 The product is preferably a hollow tube, for example, a boiler pipe having a bent portion. In these cases, the pressurization is preferably performed by applying an internal pressure to the product.
　本発明によって、加熱及び加圧により劣化した製品のクリープ余寿命の予測方法、及び、この予測方法に用いる検量線作成方法を提供することが可能となった。 According to the present invention, it is possible to provide a method for predicting the remaining creep life of a product deteriorated by heating and pressurization, and a calibration curve creating method used for this prediction method.
亀裂が生じたベイナイト組織を有する製品の模式図である。It is a schematic diagram of the product which has the bainite structure in which the crack produced. 試験２における、試料の損傷率が０の時の、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM when the damage rate of the sample in the test 2 is 0. 試験１における、試料の損傷率が０の時の、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM when the damage rate of the sample in the test 1 is 0. 試験１における、試料の損傷率が０．１２の時の、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM when the damage rate of the sample in Test 1 is 0.12. 試験１における、試料の損傷率が０．１９の時の、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM when the damage rate of the sample in Test 1 is 0.19. 試験１における、試料の損傷率が０．２６の時の、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM when the damage rate of the sample in Test 1 is 0.26. 試験１における、試料の損傷率が０．５０の時の、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM when the damage rate of the sample in Test 1 is 0.50. 試験１における、試料の損傷率が０．７０の時の、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM when the damage rate of the sample in Test 1 is 0.70. 一実施形態における、ボイド個数密度と試料の損傷率との関係を示すグラフである。It is a graph which shows the relationship between the void number density and the damage rate of a sample in one Embodiment. 試験１における試料の損傷率が０．７６の時の、（ａ）５０倍、（ｂ）１００倍、及び、（ｃ）４００倍の倍率で行った、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM performed by the magnification of (a) 50 times, (b) 100 times, and (c) 400 times when the damage rate of the sample in Test 1 is 0.76. is there. 試験１における試料の損傷率が０．８５の時の、（ａ）５０倍、（ｂ）１００倍、及び、（ｃ）４００倍の倍率で行った、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM performed by the magnification of (a) 50 times, (b) 100 times, and (c) 400 times when the damage rate of the sample in Test 1 is 0.85. is there. 試験１における試料の損傷率が１．００の時の、（ａ）１０倍、（ｂ）５０倍、（ｃ）１００倍、及び、（ｄ）４００倍の倍率で行った、ＳＥＭによる組織検査の結果を示す図である。Histological examination by SEM performed at a magnification of (a) 10 times, (b) 50 times, (c) 100 times, and (d) 400 times when the damage rate of the sample in Test 1 is 1.00 It is a figure which shows the result. 試験２における試料の損傷率が０．７０の時の、（ａ）１００倍、及び、（ｂ）４００倍の倍率で行った、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM performed by the magnification of (a) 100 time and (b) 400 time when the damage rate of the sample in Test 2 is 0.70. 試験２における試料の損傷率が０．９８の時の、（ａ）５０倍、（ｂ）１００倍、及び、（ｃ）４００倍の倍率で行った、ＳＥＭによる組織検査の結果を示す図である。It is a figure which shows the result of the structure | tissue examination by SEM performed by the magnification of (a) 50 times, (b) 100 times, and (c) 400 times when the damage rate of the sample in Test 2 is 0.98. is there. 試験２における試料の損傷率が１．００の時の、（ａ）１０倍、（ｂ）５０倍、（ｃ）１００倍、及び、（ｄ）４００倍の倍率で行った、ＳＥＭによる組織検査の結果を示す図である。Histological examination by SEM performed at magnifications of (a) 10 times, (b) 50 times, (c) 100 times, and (d) 400 times when the damage rate of the sample in Test 2 is 1.00 It is a figure which shows the result. 一実施形態における、（ａ）損傷率が０～１．０、及び、（ｂ）損傷率が０．７～１．０での、最大亀裂長さと試料の損傷率との関係を表すグラフである。FIG. 6 is a graph showing the relationship between the maximum crack length and the sample damage rate when (a) the damage rate is 0 to 1.0 and (b) the damage rate is 0.7 to 1.0 in an embodiment. is there. 一実施形態における、拡張Ｍパラメータと試料の損傷率との関係を示すグラフである。It is a graph which shows the relationship between the extended M parameter and the damage rate of a sample in one Embodiment.
　以下、本発明の実施の形態を詳細に説明する。なお、本発明の目的、特徴、利点、および、そのアイデアは、本明細書の記載により、当業者には明らかであり、本明細書の記載から、当業者であれば容易に本発明を再現できる。以下に記載された発明の実施の形態及び具体的な実施例などは、本発明の好ましい実施態様を示すものであり、例示又は説明のために示されているのであって、本発明をそれらに限定するものではない。本明細書で開示されている本発明の意図並びに範囲内で、本明細書の記載に基づき、様々な改変並びに修飾ができることは、当業者にとって明らかである。 Hereinafter, embodiments of the present invention will be described in detail. The objects, features, advantages, and ideas of the present invention will be apparent to those skilled in the art from the description of the present specification, and those skilled in the art can easily reproduce the present invention from the description of the present specification. it can. The embodiments and specific examples of the invention described below show preferred embodiments of the present invention and are shown for illustration or explanation, and the present invention is not limited to them. It is not limited. It will be apparent to those skilled in the art that various modifications and variations can be made based on the description of the present specification within the spirit and scope of the present invention disclosed herein.
　従来、フェライト、オーステナイト及びベイナイトに代表される母材は、加熱及び加圧により劣化しても、ボイドや亀裂はほとんど生じないと考えられてきた。このため、ベイナイト組織を有する製品のクリープ余寿命を、ボイドや亀裂を検出することによって予測することはなかった。
　しかし、本発明者等は、ベイナイト組織を有する製品を加熱及び加圧すると、劣化に伴ってボイドが生じ、さらに、劣化が進行するにつれてボイドが亀裂へと変化することを発見した。加えて、製品の表面に亀裂が生じていない時にはボイドに、そして、製品の表面に亀裂が生じている時には、製品に生じた亀裂のうち最大の長さを有する亀裂に着目することによって、ベイナイト組織を有する製品の余寿命を予測できることを見出した。本発明は、これらの発見に基づいて、完成されたものである。 Conventionally, it has been considered that base materials represented by ferrite, austenite, and bainite hardly cause voids or cracks even when they are deteriorated by heating and pressurization. For this reason, the creep remaining life of a product having a bainite structure has not been predicted by detecting voids or cracks.
However, the present inventors have discovered that when a product having a bainite structure is heated and pressurized, voids are generated with deterioration, and further, the voids are changed into cracks as the deterioration progresses. In addition, by focusing on voids when there are no cracks on the surface of the product, and on the cracks with the maximum length among the cracks generated on the product when the surface of the product is cracked, It was found that the remaining life of a product having an organization can be predicted. The present invention has been completed based on these findings.
＝＝＝クリープ余寿命を予測する方法に用いる検量線の作成方法＝＝＝
　本発明に係る、加熱及び加圧により劣化した第１製品のクリープ余寿命を予測する方法に用いる検量線を作成する方法は、加熱及び加圧により劣化した第２製品の表面において、任意の評価範囲を設定する工程と、評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、評価範囲内において、亀裂が生じていない場合には、評価範囲内において、ボイドの個数密度を求める工程と、得られたボイドの個数密度と第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、
　評価範囲内において、亀裂が生じている場合には、評価範囲内において生じた最大亀裂の長さを求める工程と、得られた最大亀裂長さと第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、第１製品および第２製品がベイナイト組織を有することを特徴とする。
　上述のように、ベイナイト組織を有する製品は、加熱及び加圧されると劣化に伴ってボイドが生じ、さらに、劣化が進行するにつれてボイドが亀裂へと変化するが、製品の表面に亀裂が生じているか否かに応じて、ボイドに基づいて検量線を作成するか、または、最大亀裂長さに基づいて検量線を作成するかを使い分けることによって、ベイナイト組織を有する製品の余寿命を、余寿命の値に関係なく精度良く予測することができる。 === Preparation Method of Calibration Curve Used for Predicting Creep Remaining Life ===
The method for creating a calibration curve used in the method for predicting the remaining creep life of the first product deteriorated by heating and pressurization according to the present invention can be arbitrarily evaluated on the surface of the second product deteriorated by heating and pressurization. Including a step of setting a range and a step of determining whether or not a crack has occurred within the evaluation range. If no crack has occurred within the evaluation range, the number density of voids within the evaluation range And a step of creating a calibration curve representing the relationship between the number density of the obtained voids and the damage rate of the second product,
If a crack has occurred within the evaluation range, a step for obtaining the length of the maximum crack generated within the evaluation range and a calibration curve representing the relationship between the obtained maximum crack length and the damage rate of the second product And the first product and the second product have a bainite structure.
As described above, when a product having a bainite structure is heated and pressurized, voids are generated as it deteriorates, and further, the voids change into cracks as the deterioration progresses, but cracks occur on the surface of the product. Depending on whether or not the calibration curve is created based on the void or the calibration curve is created based on the maximum crack length, the remaining life of the product having a bainite structure can be reduced. The prediction can be made with high accuracy regardless of the life value.
　第１製品及び第２製品は、ベイナイト組織を有し、かつ、加熱及び加圧によってクリープ変形を生じる材料から構成されている。このような材料として、例えば、鋳鋼が挙げられるが、これに限定されない。第１製品及び第２製品は、同じ材料から構成されていることが好ましい。
　第１製品及び第２製品の形は、特に限定されず、例えば、中空管、板、または、棒であることができるが、中空管であることが好ましい。中空管の断面は、どのような形であっても良く、例えば、円形、楕円形、または、多角形であることができるが、中空管の強度を考慮に入れれば、角を有さない円形または楕円形であることが好ましく、円形であることがより好ましい。
　このような中空管として、例えば、曲がり部分を有するボイラ用配管が挙げられる。ボイラ用配管は、従来は、フェライト組織またはパーライト組織を有すると考えられていたため、フェライト組織またはパーライト組織を有する製品のクリープ余寿命を予測する方法に従って、そのクリープ余寿命が予測されてきた。しかし、本発明者等は、ボイラ用配管の曲がり部分を作成する際のゆっくりとした冷却に伴い、この曲がり部分がベイナイト組織を有するように変化することを発見した。従って、本発明に係る検量線作成方法によって作成した検量線を用いて、曲がり部分を有するボイラ用配管のクリープ余寿命を予測すれば、このボイラ用配管のクリープ余寿命を精度良く予測することが可能となる。
　なお、第１製品の形と第２製品の形とは、同じであっても異なっていても良いが、同じまたは相似形であることが好ましく、同じであることがより好ましい。 The first product and the second product are made of a material having a bainite structure and causing creep deformation by heating and pressing. An example of such a material is cast steel, but is not limited thereto. The first product and the second product are preferably made of the same material.
The shape of the first product and the second product is not particularly limited, and can be, for example, a hollow tube, a plate, or a rod, but is preferably a hollow tube. The cross-section of the hollow tube may be any shape, for example, circular, oval, or polygonal, but with a corner if the strength of the hollow tube is taken into account. It is preferably not circular or elliptical, more preferably circular.
As such a hollow tube, for example, a boiler pipe having a bent portion can be cited. Conventionally, boiler piping has been considered to have a ferrite structure or a pearlite structure, and thus the creep remaining life has been predicted according to a method for predicting the creep remaining life of a product having a ferrite structure or pearlite structure. However, the present inventors have found that the bent portion changes to have a bainite structure with slow cooling when the bent portion of the boiler piping is created. Therefore, if the creep remaining life of a boiler pipe having a bent portion is predicted using the calibration curve created by the calibration curve creating method according to the present invention, the creep remaining life of the boiler pipe can be accurately predicted. It becomes possible.
The shape of the first product and the shape of the second product may be the same or different, but are preferably the same or similar, and more preferably the same.
　第１製品及び第２製品は、それぞれ、一定の高温、及び、常圧よりも高い一定の圧力の条件下に置くことにより劣化した製品である。
　温度の範囲は、各製品がベイナイト組織を有する限り特に限定されないが、例えば、２１０℃～５５０℃の範囲であっても良く、３５０℃～５５０℃の範囲であることが好ましい。第１製品の加熱温度と、第２製品の加熱温度とは、同じであっても異なっていても良いが、同じであることが好ましい。
　圧力の範囲は、常圧（０．１ＭＰａ）よりも高ければ特に限定されないが、例えば、０．２ＭＰａ～１０００ＭＰａであっても良く、０．３ＭＰａ～５００ＭＰａであることが好ましく、０．５ＭＰａ～３００ＭＰａであることがより好ましい。第１製品に加えられた圧力と、第２製品に加えられた圧力とは、同じであっても異なっていても良いが、同じであることが好ましい。
　製品に圧力を加える方法は、特に限定されず、外圧を加えても良く、内圧を加えても良いが、各製品が中空管である場合には内圧を加えることが好ましい。第２製品に内圧を加える場合には、内圧クリープ試験により第２製品を劣化させることが好ましい。内圧クリープ試験は、高温炉中で中空管に内圧を加え、必要に応じて中空管をクリープ破断させることによって、中空管の寿命を測定する方法である。内圧クリープ試験は、中空管そのものを試験対象とできるため、例えば中空管をボイラの配管として用いた場合に生じる、中空管の外表面および内表面の酸化物など変質層の影響を含めて試験できる点で優れている。さらに、ボイラで実際に用いられる場合と同様に、内圧による応力を中空管に加えることから、ボイラ用配管の寿命を精度よく測定することが可能である。 The first product and the second product are products deteriorated by being placed under conditions of a constant high temperature and a constant pressure higher than normal pressure, respectively.
The temperature range is not particularly limited as long as each product has a bainite structure. For example, the range may be 210 ° C. to 550 ° C., and preferably 350 ° C. to 550 ° C. The heating temperature of the first product and the heating temperature of the second product may be the same or different, but are preferably the same.
The pressure range is not particularly limited as long as it is higher than normal pressure (0.1 MPa), but may be, for example, 0.2 MPa to 1000 MPa, preferably 0.3 MPa to 500 MPa, and preferably 0.5 MPa to 300 MPa. It is more preferable that The pressure applied to the first product and the pressure applied to the second product may be the same or different, but are preferably the same.
The method of applying pressure to the product is not particularly limited, and external pressure may be applied or internal pressure may be applied. However, when each product is a hollow tube, it is preferable to apply the internal pressure. When applying an internal pressure to the second product, it is preferable to deteriorate the second product by an internal pressure creep test. The internal pressure creep test is a method of measuring the lifetime of a hollow tube by applying an internal pressure to the hollow tube in a high-temperature furnace and creeping the hollow tube as necessary. Since the internal pressure creep test can be performed on the hollow tube itself, including the effects of altered layers such as oxides on the outer surface and inner surface of the hollow tube, which occurs when the hollow tube is used as boiler piping, for example. It is excellent in that it can be tested. Further, since the stress due to the internal pressure is applied to the hollow tube in the same manner as when actually used in the boiler, it is possible to accurately measure the life of the boiler piping.
　評価範囲の設定は、第２製品の表面において、任意の広さを有する任意の箇所を選択し設定することができる。なお、広さは任意であるが、例えば、０．３ｍｍ２～１．０ｍｍ２の範囲内であっても良い。また、選択箇所は任意であるが、第２製品の表面において亀裂が生じやすい箇所であることが好ましく、当業者であれば、このような箇所を、経験則や計算から求めることができる。
　本発明に係る検量線作成方法によれば、評価範囲を任意に設定しても、ベイナイト組織を有する製品に最大亀裂長さを適用することによって、設定の仕方に依存する誤差が極めて少ない検量線を作成できるという有利な効果を奏する。従って、このようにして作成された検量線を用いれば、加熱及び加圧により劣化した第１製品のクリープ余寿命を、精度良く予測することができる。 The evaluation range can be set by selecting an arbitrary portion having an arbitrary width on the surface of the second product. Although wide is arbitrary, for example, it may be in the range of 0.3mm 2 ~ 1.0mm 2. Moreover, although a selection location is arbitrary, it is preferable that it is a location where a crack is likely to occur on the surface of the second product, and those skilled in the art can obtain such location from empirical rules and calculations.
According to the calibration curve creation method according to the present invention, even if the evaluation range is arbitrarily set, the calibration curve with very little error depending on the setting method is applied by applying the maximum crack length to the product having a bainite structure. The advantageous effect that can be created. Therefore, if the calibration curve created in this way is used, the remaining creep life of the first product deteriorated by heating and pressurization can be accurately predicted.
　設定した評価範囲内において、亀裂が生じているか否かを判定する方法は、特に限定されず、公知の方法を用いることができるが、例えば、走査型電子顕微鏡（ＳＥＭ）によって組織観察を行うことによって判定しても良い。 The method for determining whether or not a crack has occurred within the set evaluation range is not particularly limited, and a known method can be used. For example, the structure is observed with a scanning electron microscope (SEM). You may judge by.
　評価範囲内に亀裂が生じていない場合には、第２製品の表面に生じたボイドに着目して、検量線を作成する。
　評価範囲内において、ボイドの個数密度を求める方法は、特に限定されず公知の方法を用いることができるが、例えば、評価範囲内のボイドの個数を求めた後に、得られたボイド個数を評価範囲の面積で割ることによって求めることができる。これは、例えば、走査型電子顕微鏡を用いて組織観察を行うことによって求めても良い。 When no crack is generated within the evaluation range, a calibration curve is created by paying attention to voids generated on the surface of the second product.
The method for obtaining the number density of voids within the evaluation range is not particularly limited, and a known method can be used. For example, after obtaining the number of voids within the evaluation range, the number of voids obtained is evaluated within the evaluation range. It can be obtained by dividing by the area. This may be obtained, for example, by performing tissue observation using a scanning electron microscope.
　求めたボイド個数密度と第２製品の損傷率との関係を表す検量線を作成することによって、第１製品に亀裂が生じていない時の、第１製品のクリープ余寿命を予測するための検量線とすることができる。
　製品の損傷率とは、その製品の寿命に対して、寿命を決定するのと同じ加熱条件と同じ加圧条件の下でどれだけの時間が経過したのかを表す割合である。ここで、製品の寿命とは、一定の加熱及び一定の加圧によって、その製品が破断するのに要する時間である。製品の寿命は、公知の方法で求めることができ、例えば、その製品と同じ材料から作られた同一構造の製品を、実際に壊れるまで一定に加熱及び加圧することによって測定することができる。
　例えば、ある製品の寿命が１００００時間であり、寿命を決定するのと同じ加熱条件及び同じ加圧条件の下での経過時間が８０００時間である場合には、損傷率は、８０００÷１００００＝０．８０と求めることができる。逆に、ある製品の寿命が１００００であり、損傷率が０．８０の場合には、寿命を決定するのと同じ加熱条件と同じ加圧条件の下での、その製品の余寿命は、１００００ｘ０．８０＝２０００時間と求めることができる。なお、寿命を決定する条件が複数であった場合、余寿命を予測する場合の加熱条件及び加圧条件は、いずれか一つの条件に一致していれば良い。 Calibration for predicting the remaining creep life of the first product when the first product is not cracked by creating a calibration curve representing the relationship between the obtained void number density and the damage rate of the second product It can be a line.
The damage rate of a product is a ratio representing how much time has passed under the same heating condition and the same pressurizing condition as determining the lifetime with respect to the lifetime of the product. Here, the product life is the time required for the product to break by constant heating and constant pressure. The lifetime of a product can be determined by known methods, for example, by measuring a product of the same structure made from the same material as the product by constant heating and pressurization until it actually breaks.
For example, if the lifetime of a product is 10,000 hours, and the elapsed time under the same heating conditions and pressure conditions that determine the lifetime is 8000 hours, the damage rate is 8000 ÷ 10000 = 0. .80. Conversely, if the lifetime of a product is 10,000 and the damage rate is 0.80, the remaining lifetime of the product under the same heating conditions and pressure conditions that determine the lifetime is 10000 × 0 .80 = 2000 hours. In addition, when there are a plurality of conditions for determining the lifetime, the heating condition and the pressurizing condition for predicting the remaining lifetime may be any one of the conditions.
　評価範囲内に亀裂が生じている場合には、第２製品の表面に生じた最大亀裂に着目して、検量線を作成する。最大亀裂とは、評価範囲内において、加熱及び加圧による劣化に伴って製品に生じた亀裂のうち、最長の長さを有する亀裂をいう。
　亀裂が寸断されている場合には、寸断されている箇所の長さが、その寸断箇所が隣接する両亀裂のうち長い方の長さに対して所定の割合以下であれば、これら両亀裂及び寸断箇所は繋がった一つの亀裂であるとみなして、亀裂の長さを求めることが好ましい。本発明者等は、亀裂が途中で寸断されている場合において、寸断されている箇所が今後亀裂になるか否かは、この寸断箇所が隣接している両亀裂のうち長い方の亀裂から強い影響を受けることを見出した。さらに、長い方の長さに対して寸断箇所の長さが所定の割合以下である場合には、この寸断箇所が今後亀裂になりやすいと評価できることを見出した。これらの発見に基づき、寸断箇所を上記のようにみなすことによって、第１製品のクリープ余寿命を精度良く予測できる検量線を作成することが可能となる。所定の割合は、例えば、半分であることが好ましく、４割であることがより好ましく、３割であることがさらに好ましい。 When a crack is generated within the evaluation range, a calibration curve is created by paying attention to the maximum crack generated on the surface of the second product. The maximum crack means a crack having the longest length among cracks generated in a product due to deterioration due to heating and pressurization within an evaluation range.
When the crack is cut, if the length of the cut portion is equal to or less than a predetermined ratio with respect to the longer length of the two adjacent cracks, both the cracks and It is preferable to determine the length of the crack by regarding the broken portion as a single connected crack. The present inventors, in the case where the crack is broken in the middle, whether or not the broken portion will be a crack in the future is stronger from the longer of the two cracks adjacent to this broken portion Found to be affected. Furthermore, it has been found that when the length of the cut portion is equal to or less than a predetermined ratio with respect to the longer length, it can be evaluated that the cut portion is likely to crack in the future. Based on these findings, it is possible to create a calibration curve capable of accurately predicting the remaining creep life of the first product by regarding the broken portion as described above. For example, the predetermined ratio is preferably half, more preferably 40%, and still more preferably 30%.
　亀裂の長さとは、亀裂の両端を結んだ直線の長さであり、また、寸断されている箇所の長さとは、寸断されている箇所とこの寸断箇所が隣接する両亀裂とが作る２つの交点間の直線の長さである。
　亀裂の長さの求め方を、図１を用いて具体的に説明する。ベイナイト組織を有する製品１００において、亀裂１０（図１中に太い線で記載）が複数の結晶粒１に沿って生じている。亀裂１０は途中で寸断されているが、寸断されている箇所の長さ３が、この寸断箇所が隣接する両亀裂のうちの長い方の長さ４の半分以下であることから、亀裂１０は寸断箇所も含めて一つの亀裂であるとみなす。この結果、亀裂１０の長さは亀裂長さ２であると求まる。
　亀裂の長さを測定する方法は、特に限定されず、公知の方法を用いることができるが、例えば、走査型電子顕微鏡によって製品の表面の組織観察を行うことによって測定しても良い。 The length of the crack is the length of the straight line connecting the ends of the crack, and the length of the part that is cut is the two parts that the cut part and the two cracks adjacent to the cut part create. The length of a straight line between intersections.
A method of obtaining the length of the crack will be specifically described with reference to FIG. In the product 100 having a bainite structure, cracks 10 (indicated by thick lines in FIG. 1) are generated along the plurality of crystal grains 1. Although the crack 10 is cut off in the middle, the length 3 of the cut portion is less than half of the longer length 4 of the two cracks adjacent to the cut portion. Regarded as a single crack, including broken parts. As a result, the length of the crack 10 is determined to be the crack length 2.
The method for measuring the length of the crack is not particularly limited, and a known method can be used. For example, the crack length may be measured by observing the structure of the surface of the product with a scanning electron microscope.
　このようにして求めた第２製品の最大亀裂長さと損傷率との関係を表す検量線を作成することによって、第１製品において亀裂が生じている時の、第１製品のクリープ余寿命を予測するための検量線とすることができる。 By creating a calibration curve representing the relationship between the maximum crack length of the second product and the damage rate obtained in this way, the creep remaining life of the first product when a crack occurs in the first product is predicted. Can be used as a calibration curve.
　また、本発明に係る、加熱及び加圧により劣化した第１製品のクリープ余寿命を予測する方法に用いる検量線を作成する方法は、
　　加熱及び加圧により劣化した第２製品の表面において、任意の評価範囲を設定する工程と、評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、評価範囲内において、亀裂が生じていない場合には、評価範囲内において、ボイドの個数密度を求める工程と、得られたボイドの個数密度と第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、
　評価範囲内において、亀裂が生じている場合には、評価範囲内において生じた最大亀裂がまたがる結晶粒の数を求める工程と、得られた結晶粒の数と第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、第１製品および第２製品がベイナイト組織を有することを特徴としても良い。
　即ち、上述した方法において、最大亀裂長さを求める代わりに最大亀裂がまたがる結晶粒の数を求め、さらに、最大亀裂長さと第２製品の損傷率との関係を表す検量線を作成する代わりに、最大亀裂がまたがる結晶粒の数と第２製品の損傷率との関係を表す検量線を作成する。 In addition, a method for creating a calibration curve used in the method for predicting the remaining creep life of the first product deteriorated by heating and pressurization according to the present invention
Including a step of setting an arbitrary evaluation range on the surface of the second product deteriorated by heating and pressurization, and a step of determining whether or not a crack is generated within the evaluation range. In the evaluation range, the step of obtaining the number density of voids and the step of creating a calibration curve representing the relationship between the number density of the obtained voids and the damage rate of the second product are further included. Including
When cracks are generated within the evaluation range, the step of obtaining the number of crystal grains over which the maximum crack generated within the evaluation range spans, and the relationship between the number of crystal grains obtained and the damage rate of the second product And a step of creating a calibration curve representing the first product and the second product may have a bainite structure.
That is, in the above-described method, instead of obtaining the maximum crack length, the number of crystal grains spanning the maximum crack is obtained, and further, instead of creating a calibration curve representing the relationship between the maximum crack length and the damage rate of the second product. A calibration curve representing the relationship between the number of crystal grains over which the maximum crack extends and the damage rate of the second product is created.
　亀裂がまたがる結晶粒の数とは、亀裂が走る結晶粒界の面または辺の数をいう。亀裂が寸断されている場合には、寸断されている箇所の長さが、その寸断箇所が隣接する両亀裂のうち長い方の長さに対して所定の割合以下であれば、これら両亀裂及び寸断箇所は繋がった一つの亀裂であるとみなして、亀裂がまたがる結晶粒の数を求めることが好ましい。このようにみなすことによって、第１製品のクリープ余寿命を精度良く予測できる検量線とすることができる。所定の割合は、例えば、半分であることが好ましく、４割であることがより好ましく、３割であることがさらに好ましい。
　亀裂がまたがる結晶粒の数の求め方を、図１を用いて具体的に説明する。ベイナイト組織を有する製品１００において、亀裂１０（図１中に太い線で記載）が複数の結晶粒１に沿って生じている。亀裂１０は途中で寸断されているが、寸断されている箇所の長さ３が、この寸断箇所が隣接する両亀裂のうちの長い方の長さ４の半分以下であることから、亀裂１０は寸断箇所も含めて一つの亀裂であるとみなす。この結果、亀裂１０がまたがる結晶粒の数は６であると求まる。 The number of crystal grains over which a crack extends refers to the number of crystal grain boundary faces or sides where cracks run. When the crack is cut, if the length of the cut portion is equal to or less than a predetermined ratio with respect to the longer length of the two adjacent cracks, both the cracks and It is preferable to determine the number of crystal grains over which the crack extends, assuming that the broken portion is one connected crack. By considering in this way, it is possible to obtain a calibration curve that can accurately predict the remaining creep life of the first product. For example, the predetermined ratio is preferably half, more preferably 40%, and still more preferably 30%.
A method for obtaining the number of crystal grains over which a crack will straddle will be specifically described with reference to FIG. In the product 100 having a bainite structure, cracks 10 (indicated by thick lines in FIG. 1) are generated along the plurality of crystal grains 1. Although the crack 10 is cut off in the middle, the length 3 of the cut portion is less than half of the longer length 4 of the two cracks adjacent to the cut portion. Regarded as a single crack, including broken parts. As a result, the number of crystal grains over which the crack 10 extends is determined to be 6.
　亀裂がまたがる結晶粒の数を測定する方法は、特に限定されず、公知の方法を用いることができるが、例えば、走査型電子顕微鏡によって製品の表面の組織観察を行うことによって測定しても良い。
　本発明に係る検量線作成方法によれば、ベイナイト組織を有する製品の余寿命の予測するにあたって、最大亀裂がまたがる結晶粒の数を適用することによって、評価範囲を任意に設定しても、設定の仕方に依存する誤差が極めて少ない検量線を作成できるという有利な効果を奏する。 The method for measuring the number of crystal grains over which cracks cross is not particularly limited, and a known method can be used. For example, the number of crystal grains may be measured by observing the structure of the surface of the product with a scanning electron microscope. .
According to the calibration curve creation method according to the present invention, in predicting the remaining life of a product having a bainite structure, even if the evaluation range is arbitrarily set by applying the number of crystal grains over which the maximum crack extends, it is set. This produces an advantageous effect that a calibration curve with very little error depending on the method can be created.
　このようにして得られた最大亀裂がまたがる結晶粒の数と、第２製品の損傷率との関係を表す検量線を作成することによって、第１製品に亀裂が生じていない時の、第１製品のクリープ余寿命を予測するための検量線とすることができる。 By creating a calibration curve representing the relationship between the number of crystal grains spanned by the maximum crack thus obtained and the damage rate of the second product, the first product when no crack is generated in the first product is obtained. It can be a calibration curve for predicting the remaining creep life of the product.
　上述した全ての方法において、第２製品として、１種類の製品のみを用いても良く、互いに異なる温度で加熱され、かつ、互いに異なる圧力で加圧された少なくとも２種類の製品を用いても良い。この場合、これら２種類の製品のそれぞれについて、ボイド個数密度、最大亀裂長さ、および／または、最大亀裂がまたがる結晶粒の数を適宜求め、求めた全てのボイド個数密度、最大亀裂長さ、および／または、最大亀裂がまたがる結晶粒の数を用いて第２製品の損傷率との関係を求めることによって、検量線を作成する。加熱加圧条件が異なる少なくとも２種類の製品を用いて検量線を作成することによって、検量線の精度を向上させることができる。
　加熱加圧条件が異なる少なくとも２種類の製品を用いる場合、これら製品の寿命が、同程度であることが好ましい。同程度とは、２種類以上の製品の寿命が、最も長い製品の寿命を基準として他の製品の寿命が２５％以内の差であることが好ましく、２０％以内の差であることがより好ましく、１０％以内の差であることがさらに好ましい。当業者であれば、２種類以上の製品の寿命が同程度となるように、各製品に加える温度と圧力とを適切に設定することができる。
　例えば、本願の実施例１及び実施例３では、５５０℃で加熱し１４５ＭＰａで加圧した製品と、５２５℃で加熱し２４０ＭＰａで加圧した製品との２種類の製品を用い、これらに共通する関係として、図９に示す近似曲線を、ボイド個数密度と第２製品の損傷率との関係を表す検量線として得た。また、図１６に示す近似曲線を、最大亀裂長さと第２製品の損傷率との関係を表す検量線として得、図１７に示す近似曲線を、最大亀裂がまたがる結晶粒の数と第２製品の損傷率との関係を表す検量線として得た。 In all the methods described above, only one type of product may be used as the second product, or at least two types of products heated at different temperatures and pressurized at different pressures may be used. . In this case, for each of these two types of products, the void number density, the maximum crack length, and / or the number of crystal grains spanning the maximum crack are appropriately determined, and all the obtained void number densities, the maximum crack length, A calibration curve is created by determining the relationship with the damage rate of the second product using the number of grains over which the maximum crack spans. By creating a calibration curve using at least two types of products with different heating and pressing conditions, the accuracy of the calibration curve can be improved.
When at least two types of products having different heating and pressing conditions are used, it is preferable that the lifetimes of these products are comparable. The same level means that the life of two or more types of products is preferably a difference of 25% or less, more preferably a difference of 20% or less, based on the life of the longest product. More preferably, the difference is within 10%. A person skilled in the art can appropriately set the temperature and pressure applied to each product so that two or more types of products have the same life.
For example, in Example 1 and Example 3 of the present application, two types of products, that is, a product heated at 550 ° C. and pressurized at 145 MPa and a product heated at 525 ° C. and pressurized at 240 MPa are used, which are common to these. As a relationship, the approximate curve shown in FIG. 9 was obtained as a calibration curve representing the relationship between the void number density and the damage rate of the second product. Also, the approximate curve shown in FIG. 16 is obtained as a calibration curve representing the relationship between the maximum crack length and the damage rate of the second product, and the approximate curve shown in FIG. 17 is obtained from the number of crystal grains spanning the maximum crack and the second product. It was obtained as a calibration curve representing the relationship with the damage rate.
　このようにして作成した検量線を用いて、加熱及び加圧により劣化した第１製品のクリープ余寿命を予測することができる。 Using the calibration curve created in this manner, the remaining creep life of the first product deteriorated by heating and pressurization can be predicted.
＝＝＝クリープ余寿命を予測する方法＝＝
　本発明に係る加熱及び加圧により劣化した製品のクリープ余寿命を予測する方法は、製品の表面において、任意の評価範囲を設定する工程と、評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、評価範囲内において、亀裂が生じていない場合には、評価範囲内において、ボイドの個数密度を求める工程と、得られたボイドの個数密度から前記製品の損傷率を求める工程とをさらに含み、
　評価範囲内において、亀裂が生じている場合には、評価範囲内において生じた最大亀裂の長さを求める工程と、得られた最大亀裂長さから製品の損傷率を求める工程とをさらに含み、製品がベイナイト組織を有することを特徴とする。
　例えば、加熱及び加圧により劣化した第１製品のクリープ余寿命を予測するには、以下のようにして行う。
　まず、第１製品の表面において、任意の評価範囲を設定する。次いで、この評価範囲内に亀裂が生じているか否かを判定する。亀裂が生じていない場合には、第１製品の表面に存在するボイドに基づいてクリープ余寿命を予測する。即ち、まず、評価範囲内における、ボイドの個数密度を求め、得られたボイドの個数密度を、上述の方法によって作成した検量線のボイド個数密度に代入することによって、対応する損傷率を得ることができる。例えば、対応する損傷率が０．４０であると求まった場合には、第１製品の余寿命は、これまでに加熱及び加圧した時間の１．５倍であると予測することができる。
　また、もし、評価範囲内に亀裂が生じている場合には、第１製品の表面に生じている最大亀裂長さに基づいてクリープ余寿命を予測する。即ち、まず、評価範囲内における、第１製品に生じた最大亀裂の長さを求める。次いで、得られた最大亀裂長さを、上述の方法によって作成した検量線の最大亀裂長さに挿入することによって、対応する製品の損傷率を求めることができる。例えば、対応する損傷率が０．８０であると求まった場合には、第１製品の余寿命は、これまでに加熱及び加圧した時間の２５％であると予測することができる。 === Method for predicting the remaining creep life ==
The method for predicting the creep remaining life of a product deteriorated by heating and pressurization according to the present invention includes a step of setting an arbitrary evaluation range on the surface of the product, and whether or not a crack is generated within the evaluation range. And determining the number of voids within the evaluation range, and determining the damage rate of the product from the obtained number density of voids. And further comprising a process,
In the evaluation range, when a crack has occurred, the method further includes a step of determining the length of the maximum crack generated in the evaluation range, and a step of determining a product damage rate from the obtained maximum crack length, The product is characterized by having a bainite structure.
For example, in order to predict the remaining creep life of the first product that has deteriorated due to heating and pressurization, the following is performed.
First, an arbitrary evaluation range is set on the surface of the first product. Next, it is determined whether or not a crack has occurred within this evaluation range. If no crack has occurred, the remaining creep life is predicted based on the voids present on the surface of the first product. That is, first, the number density of voids within the evaluation range is obtained, and the obtained damage number density is obtained by substituting the obtained number density of voids into the void number density of the calibration curve prepared by the above-described method. Can do. For example, if the corresponding damage rate is determined to be 0.40, the remaining life of the first product can be predicted to be 1.5 times the time of heating and pressurization so far.
Further, if a crack is generated within the evaluation range, the remaining creep life is predicted based on the maximum crack length generated on the surface of the first product. That is, first, the length of the maximum crack generated in the first product within the evaluation range is obtained. Then, by inserting the obtained maximum crack length into the maximum crack length of the calibration curve created by the above-described method, the damage rate of the corresponding product can be obtained. For example, if the corresponding damage rate is determined to be 0.80, the remaining life of the first product can be predicted to be 25% of the time of heating and pressurization so far.
　また、本発明に係る加熱及び加圧により劣化した製品のクリープ余寿命を予測する方法は、評価範囲内に亀裂が生じている場合には、「評価範囲内において生じた最大亀裂の長さを求める工程と、得られた最大亀裂長さから製品の損傷率を求める工程とをさらに含む」代わりに、「評価範囲内において生じた最大亀裂がまたがる結晶粒の数を求める工程と、得られた結晶粒の数からその製品の損傷率を求める工程とをさらに含む」ことを特徴としても良い。
　この場合、例えば、加熱及び加圧により劣化した第１製品のクリープ余寿命を予測するには、以下のようにして行う。まず、第１製品に生じた最大亀裂がまたがる結晶粒の数を求める。次いで、得られた結晶粒の数を、上述の方法によって作成した検量線における、最大亀裂がまたがる結晶粒の数に挿入する。これにより、対応する製品の損傷率を求めることができる。 In addition, the method for predicting the remaining creep life of a product deteriorated by heating and pressurization according to the present invention is as follows: When a crack is generated within the evaluation range, the length of the maximum crack generated within the evaluation range is determined. Instead of “obtaining the step of determining the damage rate of the product from the obtained maximum crack length” and “determining the number of crystal grains over which the maximum crack generated within the evaluation range spans” And a step of obtaining a damage rate of the product from the number of crystal grains ”.
In this case, for example, in order to predict the remaining creep life of the first product deteriorated by heating and pressurization, the following is performed. First, the number of crystal grains over which the maximum crack generated in the first product extends is obtained. Next, the number of crystal grains obtained is inserted into the number of crystal grains across the maximum crack in the calibration curve created by the above-described method. Thereby, the damage rate of the corresponding product can be obtained.
　これら本発明に係る「クリープ余寿命を予測する方法」は、上記「クリープ余寿命を予測する方法に用いる検量線の作成方法」を参照しながら、当業者であれば、適宜適切に実施することができる。 These “methods for predicting the remaining creep life” according to the present invention should be appropriately carried out by those skilled in the art as appropriate while referring to the “method for preparing a calibration curve used in the method for predicting the remaining creep life”. Can do.
［実施例１］
　クロムモリブデン鉄鋼鋼材から作られたベイナイト組織を有する円筒管（ＳＴＰＡ２２、外径φ５６．５ｍｍ、内径４７．５ｍｍ、長さ３５．０ｍｍ）を試料として、内圧クリープ試験を行った。１つの試料には、温度５５０℃の条件下で１４５ＭＰａの内圧を加え（試験１）、別の試料には、温度５２５℃の条件下で２４０ＭＰａの内圧を加えた（試験２）。なお、試験１における試料の寿命と、試験２における試料の寿命とは、試験１における試料に対して、試験２における試料の寿命は約２３％短く、同程度であった。 [Example 1]
An internal pressure creep test was carried out using a cylindrical tube (STPA 22, outer diameter φ56.5 mm, inner diameter 47.5 mm, length 35.0 mm) made of chromium molybdenum steel and having a bainite structure as a sample. One sample was subjected to an internal pressure of 145 MPa at a temperature of 550 ° C. (Test 1), and another sample was subjected to an internal pressure of 240 MPa at a temperature of 525 ° C. (Test 2). The life of the sample in Test 1 and the life of the sample in Test 2 were about the same as the life of the sample in Test 2, which was about 23% shorter than that of the sample in Test 1.
　試験１については、損傷率が、０、０．１２、０．１９、０．２６、０．５０および０．７０の時に、また、試験２については、損傷率が、０．００、０．１４、０．２３、０．３２および０．６１の時に、走査型電子顕微鏡（ＳＥＭ）を用いて試料の組織観察を行った。
　具体的には、各試料について、１．０ｍｍ２の広さを有する任意の評価範囲を定め、この評価範囲について、１００倍、５００倍及び１０００倍の倍率で組織観察をし、ボイドの数を調べた。なお、評価範囲の選択の仕方によって大きな誤差が生じないことを示すべく、１．０ｍｍ２の広さを有する評価範囲の中から、０．３ｍｍ２の広さを有する評価範囲をさらに設定し、この小さな評価範囲についても組織観察を行い、ボイドの数を調べた。 For test 1, the damage rates were 0, 0.12, 0.19, 0.26, 0.50, and 0.70, and for test 2, the damage rates were 0.00, 0,. At 14, 0.23, 0.32, and 0.61, the structure of the sample was observed using a scanning electron microscope (SEM).
Specifically, for each sample, an arbitrary evaluation range having a width of 1.0 mm 2 is determined, and the structure is observed at magnifications of 100 times, 500 times, and 1000 times, and the number of voids is determined. Examined. In order to show that a large error does not occur depending on how the evaluation range is selected, an evaluation range having a width of 0.3 mm 2 is further set from the evaluation range having a width of 1.0 mm 2 . The structure was also observed in this small evaluation range, and the number of voids was examined.
　得られたＳＥＭの結果のうち、代表して、試験２における損傷率が０．０の時のＳＥＭの像を図２に、試験１における各損傷率時のＳＥＭの像を図３～図８に示す。また、図３～図８の結果から求めた、ボイドの個数と、ボイド個数を評価範囲の面積で割ったボイド個数密度（個／ｍｍ２）と、ボイド個数密度平均値（個／ｍｍ２）とを、表１に示す。
　そして、全てのＳＥＭの結果から求めた、ボイド個数密度平均値と損傷率との関係を、図９に示す。なお、全てのＳＥＭの結果において、亀裂は生じていなかった。 Of the obtained SEM results, representatively, SEM images when the damage rate in Test 2 is 0.0 are shown in FIG. 2, and SEM images at each damage rate in Test 1 are shown in FIGS. Shown in Moreover, was determined from the results of FIGS. 3-8, the number of voids, the void number density divided by the void number in the area of the evaluation range (number / mm 2), the void number density average value (number / mm 2) Is shown in Table 1.
FIG. 9 shows the relationship between the average number of voids and the damage rate obtained from all SEM results. In all SEM results, no cracks occurred.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１及び図９が示すように、ボイドの個数密度を用いることによって、特に製品の表面に亀裂は生じていない場合に、ベイナイト組織を有する製品のクリープ余寿命を精度良く予測できる。
　また、全てのＳＥＭの結果から求めた、ボイドの個数密度と損傷率との関係を示す図９を用いることによって、実施例１で使用した試料と同一の材料から作られた、ベイナイト組織を有する他の製品のクリープ余寿命を予測することができ、特に、製品の表面に亀裂が生じていない場合に、より精度良くクリープ余寿命を予測することができる。 As shown in Table 1 and FIG. 9, by using the number density of voids, it is possible to accurately predict the remaining creep life of a product having a bainite structure, particularly when there is no crack on the surface of the product.
Moreover, it has the bainite structure | tissue made from the same material as the sample used in Example 1 by using FIG. 9 which shows the relationship between the number density of a void and the damage rate calculated | required from the result of all SEM. The remaining creep life of other products can be predicted. In particular, when there is no crack on the surface of the product, the remaining creep life can be predicted with higher accuracy.
　［実施例２］
　実施例２では、実施例１で作成した図９を用いて、ベイナイト組織を有する円筒管のクリープ余寿命を予測した。
　クロムモリブデン鉄鋼鋼材で作られた配管（ＳＴＰＡ２２、ＪＩＳ規格　Ｇ　３４５７「配管用アーク溶接炭素鋼鋼管」）を、火力発電所のボイラで使用できるように、ゆっくりと加熱しながら曲げ加工した。加工した配管の曲がり部分の組織をＳＥＭで検査したところ、ベイナイト組織が生成していた。このようにして加工した配管に対し、５５０℃の温度下で、１４５ＭＰａの内圧を加えた。 [Example 2]
In Example 2, the remaining creep life of a cylindrical tube having a bainite structure was predicted using FIG. 9 created in Example 1.
A pipe made of chromium molybdenum steel (STPA 22, JIS standard G 3457 “arc welded carbon steel pipe for piping”) was bent while being heated slowly so that it could be used in a boiler of a thermal power plant. When the structure of the bent portion of the processed pipe was inspected by SEM, a bainite structure was generated. An internal pressure of 145 MPa was applied to the pipe thus processed at a temperature of 550 ° C.
　ある時間経過したところで、配管の曲がり部分について、ＳＥＭを用いて組織観察した。得られたＳＥＭの像を解析したところ、この曲がり部分の表面に亀裂が生じていないことが分かったので、ＳＥＭの像からボイド個数密度を求めたところ、５０であった。
　実施例１で作成した図９より、ボイド個数密度が５０の時の損傷率は０．４１であると求まることから、ボイラの配管の曲がり部分の損傷率は０．４１であると予測することができた。即ち、この配管の曲がり部分の余寿命は、現在までの使用時間の約２．５倍であると予測することができた。 After a certain period of time, the structure of the bent portion of the piping was observed using SEM. When the obtained SEM image was analyzed, it was found that no crack was generated on the surface of the bent portion. Therefore, the void number density was determined from the SEM image and found to be 50.
From FIG. 9 created in Example 1, since the damage rate when the void number density is 50 is found to be 0.41, it is predicted that the damage rate of the bent portion of the boiler piping is 0.41. I was able to. In other words, it was possible to predict that the remaining life of the bent portion of this pipe was about 2.5 times the usage time up to now.
［実施例３］
　実施例１と同様の条件で、クロムモリブデン鉄鋼鋼材から作られたベイナイト組織を有する円筒管（ＳＴＰＡ２２、外径φ５６．５ｍｍ、内径４７．５ｍｍ、長さ３５．０ｍｍ）を試料として、内圧クリープ試験を行った。１つの試料には、温度５５０℃の条件下で１４５ＭＰａの内圧を加え（試験１）、別の試料には、温度５２５℃の条件下で２４０ＭＰａの内圧を加えた（試験２）。なお、試験１における試料の寿命と、試験２における試料の寿命とは、試験１における試料に対して、試験２における試料の寿命は約２３％短く、同程度であった。 [Example 3]
An internal pressure creep test using a cylindrical tube (STPA 22, outer diameter φ56.5 mm, inner diameter 47.5 mm, length 35.0 mm) having a bainite structure made of chromium molybdenum steel material under the same conditions as in Example 1 Went. One sample was subjected to an internal pressure of 145 MPa at a temperature of 550 ° C. (Test 1), and another sample was subjected to an internal pressure of 240 MPa at a temperature of 525 ° C. (Test 2). The life of the sample in Test 1 and the life of the sample in Test 2 were about the same as the life of the sample in Test 2, which was about 23% shorter than that of the sample in Test 1.
　試験１については、損傷率が、０、０．１１、０．１８、０．２５、０．４７、０．６６、０．７６、０．８５および１．００の時に、また、試験２については、損傷率が、０．００、０．１４、０．２３、０．３２、０．６１、０．８５、０．９８および１．００の時に、試料の組織観察を行った。
　具体的には、各試料について、観察毎に評価範囲を定めた。評価範囲の位置の設定は、円筒管において亀裂が生じやすいとされる管の長さ方向の中央部分を含むように設定した。また、評価範囲の面積の設定は、亀裂が１．０ｍｍ２以上の面積にわたる場合には亀裂全体を含むように定め、これ以外の場合には０．３ｍｍ２または１．０ｍｍ２の広さを有するように設定した。
　定めた評価範囲について、１０倍、５０倍、１００倍及び４００倍の倍率で走査型電子顕微鏡（ＳＥＭ）を用いて組織観察をし、評価範囲内に存在するボイドの数、さらに、亀裂が存在した場合には、最も長い亀裂について、最大亀裂長さ、及び、最大亀裂がまたがる結晶粒の数（以下、「拡張Ｍパラメータ」ともいう）を測定した。なお、亀裂が途中で寸断されていた場合には、その寸断されている箇所の各長さが、寸断箇所が隣接する両亀裂のうち長い方の長さの半分以下であれば、これらの亀裂及び寸断箇所は繋がった一つの亀裂であるとみなして、最大亀裂長さ及び拡張Ｍパラメータを求めた。 For test 1, when the damage rate is 0, 0.11, 0.18, 0.25, 0.47, 0.66, 0.76, 0.85 and 1.00, and for test 2 Observed the structure of the sample when the damage rate was 0.00, 0.14, 0.23, 0.32, 0.61, 0.85, 0.98, and 1.00.
Specifically, an evaluation range was determined for each observation for each sample. The position of the evaluation range was set so as to include a central portion in the length direction of the pipe, which is likely to cause cracks in the cylindrical pipe. The setting of the area of the evaluation range is determined as if the crack extends over 1.0 mm 2 or more areas comprises the entire crack, the size of 0.3 mm 2 or 1.0 mm 2 in other cases Set to have.
For the defined evaluation range, the structure is observed with a scanning electron microscope (SEM) at magnifications of 10 times, 50 times, 100 times, and 400 times, and the number of voids present in the evaluation range and cracks are present. In this case, for the longest crack, the maximum crack length and the number of crystal grains over which the maximum crack crosses (hereinafter also referred to as “extended M parameter”) were measured. In addition, when the crack is cut off in the middle, if each length of the cut-off portion is less than half of the longer one of the two cracks adjacent to the cut-off portion, these cracks The maximum crack length and the extended M parameter were determined by regarding the severed portion as one connected crack.
　得られたＳＥＭの像のうち、亀裂が生じていた像を図１０～図１５に示す。具体的には、試験１における損傷率が０．７６の像を図１０に、損傷率が０．８５の像を図１１に、及び、損傷率が１．００の像を図１２に、並びに、試験２における損傷率が０．７０の像を図１３に、損傷率が０．９８の像を図１４に、及び、損傷率が１．００の像を図１５に示す。
　例えば図１０（ｂ）が示すように、試験１における損傷率が０．７６の時の最大亀裂は、途中で寸断されているが、寸断されている箇所の長さが、隣接する両亀裂のうち長い方の長さの半分以下であったため、これらの亀裂及び寸断箇所は繋がった一つの亀裂であるとみなして、最大亀裂長さを５１８μｍと求め、拡張Ｍパラメータを６と求めた。同様に、図１１（ａ）が示すように、試験１における損傷率が０．８５の時の最大亀裂は、複数個所が途中で寸断されているが、寸断されている各箇所の長さが、それぞれが隣接する両亀裂のうち長いほうの亀裂の長さの半分以下であったため、これらの亀裂及び寸断箇所は繋がった一つの亀裂であるとみなして、最大亀裂長さを１．０９ｍｍと求め、拡張Ｍパラメータを１４と求めた。 Of the obtained SEM images, cracked images are shown in FIGS. Specifically, an image with a damage rate of 0.76 in Test 1 is shown in FIG. 10, an image with a damage rate of 0.85 is shown in FIG. 11, an image with a damage rate of 1.00 is shown in FIG. FIG. 13 shows an image with a damage rate of 0.70 in Test 2, FIG. 14 shows an image with a damage rate of 0.98, and FIG. 15 shows an image with a damage rate of 1.00.
For example, as shown in FIG. 10 (b), the maximum crack when the damage rate in Test 1 is 0.76 is cut off in the middle, but the length of the cut-off portion is the length of both adjacent cracks. Since it was less than half the length of the longer one, these cracks and cut portions were regarded as one connected crack, the maximum crack length was determined to be 518 μm, and the extended M parameter was determined to be 6. Similarly, as shown in FIG. 11 (a), the maximum crack when the damage rate in Test 1 is 0.85 is cut off at a plurality of locations, but the length of each cut-off location is Since each of the adjacent cracks was less than half of the length of the longer crack, the crack and the cut portion were regarded as one connected crack, and the maximum crack length was 1.09 mm. The extended M parameter was determined to be 14.
　このようにして、全てのＳＥＭの像から求めたボイドの数、ボイドの数を評価範囲の面積で割ったボイド個数密度、ボイド個数密度の平均値、最大亀裂長さ及び拡張Ｍパラメータの結果を、試験１については表２に、試験２については表３にまとめて示す。 Thus, the number of voids obtained from all SEM images, the void number density obtained by dividing the number of voids by the area of the evaluation range, the average value of the void number density, the maximum crack length, and the extended M parameter results are obtained. Test 1 is summarized in Table 2, and Test 2 is summarized in Table 3.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　さらに、表２及び表３に基づいて作成した、最大亀裂長さと損傷率との関係を表すグラフを図１６に、拡張Ｍパラメータと損傷率との関係を表すグラフを図１７に示す。
　１６及び図１７が示すように、ボイド個数密度を使用してベイナイト組織を有する製品のクリープ余寿命を予測すれば、特に製品の表面に亀裂は生じていない場合に、クリープ余寿命を精度良く予測できる。
　また、図１６及び図１７が示すように、最大亀裂が途中で寸断されている場合に、寸断されている箇所の各長さが、寸断箇所が隣接する両亀裂のうち長い方の長さの半分以下であれば、これらの亀裂及び寸断箇所は繋がった一つの亀裂であるとみなした最大亀裂長さを採用することによって、最大亀裂長さと損傷率との間、及び、拡張Ｍパラメータと損傷率との間には、良好な相関関係が存在することが分かる。即ち、これら、最大亀裂長さと損傷率との関係を表す図１６、および／または、拡張Ｍパラメータと損傷率との関係を表す図１７を用いることによって、実施例３で使用した試料と同一の材料から作られた、ベイナイト組織を有する他の製品のクリープ余寿命を予測することができ、特に、製品の表面に亀裂が生じている場合に、より精度良くクリープ余寿命を予測することができる。 Further, FIG. 16 shows a graph representing the relationship between the maximum crack length and the damage rate created based on Tables 2 and 3, and FIG. 17 shows a graph representing the relationship between the extended M parameter and the damage rate.
As shown in FIG. 16 and FIG. 17, if the creep remaining life of a product having a bainite structure is predicted using the void number density, the remaining creep life is accurately predicted, particularly when there is no crack on the surface of the product. it can.
As shown in FIGS. 16 and 17, when the maximum crack is cut in the middle, each length of the cut-off portion is the longer of the two cracks adjacent to the cut-off portion. If less than half, these cracks and breaks are between the maximum crack length and the damage rate, and the extended M parameter and damage by adopting the maximum crack length that is considered to be one connected crack. It can be seen that there is a good correlation with the rate. That is, by using FIG. 16 showing the relationship between the maximum crack length and the damage rate and / or FIG. 17 showing the relationship between the extended M parameter and the damage rate, the same sample as that used in Example 3 was used. It is possible to predict the remaining creep life of other products made of materials and having a bainite structure. In particular, when the surface of the product is cracked, the remaining creep life can be predicted more accurately. .
　［実施例４］
　実施例４では、実施例３で作成した図１６及び図１７を用いて、ベイナイト組織を有する円筒管のクリープ余寿命を予測した。
　クロムモリブデン鉄鋼鋼材で作られた配管（ＳＴＰＡ２２、ＪＩＳ規格　Ｇ　３４５７「配管用アーク溶接炭素鋼鋼管」）を、火力発電所のボイラで使用できるように、ゆっくりと加熱しながら曲げ加工した。加工した配管の曲がり部分の組織をＳＥＭで検査したところ、ベイナイト組織が生成していた。このようにして加工した配管に対し、５５０℃の温度下で、１４５ＭＰａの内圧を加えた。 [Example 4]
In Example 4, the remaining creep life of a cylindrical tube having a bainite structure was predicted using FIGS. 16 and 17 created in Example 3. FIG.
A pipe made of chromium molybdenum steel (STPA 22, JIS standard G 3457 “arc welded carbon steel pipe for piping”) was bent while being heated slowly so that it could be used in a boiler of a thermal power plant. When the structure of the bent portion of the processed pipe was inspected by SEM, a bainite structure was generated. An internal pressure of 145 MPa was applied to the pipe thus processed at a temperature of 550 ° C.
　ある時間経過したところで、配管の曲がり部分について、ＳＥＭを用いて組織観察した。得られたＳＥＭの像を解析したところ、この曲がり部分の表面に亀裂が生じていることが分かったので、ＳＥＭの像から最大亀裂長さを求めた結果、１．７ｍｍであった。実施例１で作成した図１６より、最大亀裂長さが１．７ｍｍの時の損傷率は０．９５であると求まることから、ボイラの配管の曲がり部分の損傷率は０．９５であると予測することができた。即ち、この配管の曲がり部分の余寿命は、現在までの使用時間の約５％であると予測することができた。 After a certain period of time, the bent part of the pipe was observed with a SEM. When the obtained SEM image was analyzed, it was found that a crack was generated on the surface of the bent portion. Therefore, the maximum crack length was determined from the SEM image, and the result was 1.7 mm. From FIG. 16 created in Example 1, since the damage rate when the maximum crack length is 1.7 mm is found to be 0.95, the damage rate of the bent portion of the boiler piping is 0.95. I was able to predict. That is, the remaining life of the bent portion of the pipe could be predicted to be about 5% of the usage time up to now.
　同様にして、得られたＳＥＭの像から拡張Ｍパラメータを求めたところ、２５であった。実施例１で作成した図１７より、拡張Ｍパラメータが２５の時の損傷率は０．９５であると求まることから、ボイラの配管の曲がり部分の損傷率は０．９５であると予測することができた。即ち、この配管の曲がり部分の余寿命は、現在までの使用時間の約５％であると予測することができた。 Similarly, when the extended M parameter was obtained from the obtained SEM image, it was 25. From FIG. 17 created in Example 1, since the damage rate when the extended M parameter is 25 is found to be 0.95, it is predicted that the damage rate of the bent portion of the boiler piping is 0.95. I was able to. That is, the remaining life of the bent portion of the pipe could be predicted to be about 5% of the usage time up to now.
　　１　結晶粒
　　２　亀裂長さ
　　３　寸断されている箇所の長さ
　　４　寸断箇所が隣接する亀裂のうち長い方の長さ
　１０　亀裂
１００　ベイナイト組織を有する製品 DESCRIPTION OF SYMBOLS 1 Crystal grain 2 Crack length 3 The length of the part cut off 4 The length of the longer one among the cracks where the cut off part adjoins 10 Crack 100 The product which has a bainite structure

Claims (18)

  1. 　加熱及び加圧により劣化した第１製品のクリープ余寿命を予測する方法に用いる検量線を作成する方法であって、
    　　加熱及び加圧により劣化した第２製品の表面において、任意の評価範囲を設定する工程と、
    　　前記評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、
    　　前記評価範囲内において、亀裂が生じていない場合には、
    　　　前記評価範囲内において、ボイドの個数密度を求める工程と、
    　　　得られたボイドの個数密度と第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、
    　　前記評価範囲内において、亀裂が生じている場合には、
    　　　前記評価範囲内において生じた最大亀裂の長さを求める工程と、
    　　　得られた最大亀裂長さと第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、
    　第１製品および第２製品がベイナイト組織を有することを特徴とする、検量線の作成方法。     A method for creating a calibration curve used in a method for predicting the remaining creep life of a first product deteriorated by heating and pressurization,
    A step of setting an arbitrary evaluation range on the surface of the second product deteriorated by heating and pressurization;
    Determining whether or not a crack has occurred within the evaluation range,
    Within the evaluation range, if no cracks have occurred,
    Within the evaluation range, obtaining a void number density;
    A step of creating a calibration curve representing the relationship between the number density of the obtained voids and the damage rate of the second product,
    In the evaluation range, if a crack has occurred,
    A step of determining the length of the maximum crack generated within the evaluation range;
    Creating a calibration curve representing the relationship between the obtained maximum crack length and the damage rate of the second product,
    A method for preparing a calibration curve, wherein the first product and the second product have a bainite structure.
  2. 　加熱及び加圧により劣化した第１製品のクリープ余寿命を予測する方法に用いる検量線を作成する方法であって、
    　　加熱及び加圧により劣化した第２製品の表面において、任意の評価範囲を設定する工程と、
    　　前記評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、
    　　前記評価範囲内において、亀裂が生じていない場合には、
    　　　前記評価範囲内において、ボイドの個数密度を求める工程と、
    　　　得られたボイドの個数密度と第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、
    　　前記評価範囲内において、亀裂が生じている場合には、
    　　　前記評価範囲内において生じた最大亀裂がまたがる結晶粒の数を求める工程と、
    　　　得られた結晶粒の数と第２製品の損傷率との関係を表す検量線を作成する工程とをさらに含み、
    　第１製品および第２製品がベイナイト組織を有することを特徴とする、検量線の作成方法。     A method for creating a calibration curve used in a method for predicting the remaining creep life of a first product deteriorated by heating and pressurization,
    A step of setting an arbitrary evaluation range on the surface of the second product deteriorated by heating and pressurization;
    Determining whether or not a crack has occurred within the evaluation range,
    Within the evaluation range, if no cracks have occurred,
    Within the evaluation range, obtaining a void number density;
    A step of creating a calibration curve representing the relationship between the number density of the obtained voids and the damage rate of the second product,
    In the evaluation range, if a crack has occurred,
    Determining the number of crystal grains spanned by the maximum crack generated within the evaluation range;
    A step of creating a calibration curve representing the relationship between the number of obtained crystal grains and the damage rate of the second product,
    A method for preparing a calibration curve, wherein the first product and the second product have a bainite structure.
  3. 　前記評価範囲を、第２製品の表面において亀裂が生じやすい箇所に設定することを特徴とする、請求項１または２に記載の検量線の作成方法。 3. The method for creating a calibration curve according to claim 1 or 2, wherein the evaluation range is set at a location where a crack is likely to occur on the surface of the second product.
  4. 　最大亀裂が寸断されている場合に、寸断されている各箇所の長さが、その寸断箇所が隣接する両亀裂のうち長い方の長さに対して所定の割合以下であれば、最大亀裂は寸断されていないものとみなして、最大亀裂長さ、または、最大亀裂がまたがる結晶粒の数を求めることを特徴とする、請求項１～３のいずれか１項に記載の検量線作成方法。 When the maximum crack is cut, if the length of each cut portion is less than a predetermined ratio with respect to the longer length of the two adjacent cracks, the maximum crack is The calibration curve creation method according to any one of claims 1 to 3, wherein the maximum crack length or the number of crystal grains over which the maximum crack crosses is determined on the assumption that it is not broken.
  5. 　所定の割合が半分であることを特徴とする、請求項４に記載の検量線作成方法。 5. The calibration curve creation method according to claim 4, wherein the predetermined ratio is half.
  6. 　第１製品および第２製品が、中空管であることを特徴とする、請求項１～５のいずれか１項に記載の検量線作成方法。 6. The calibration curve generating method according to claim 1, wherein the first product and the second product are hollow tubes.
  7. 　第１製品および第２製品が、曲がり部分を有するボイラ用配管であることを特徴とする、請求項６に記載の検量線作成方法。 The calibration curve creation method according to claim 6, wherein the first product and the second product are boiler pipes having a bent portion.
  8. 　前記加圧が内圧を加えることにより行われることを特徴とする、請求項６または７に記載の検量線作成方法。 The calibration curve creating method according to claim 6 or 7, wherein the pressurization is performed by applying an internal pressure.
  9. 　第２製品として、互いに異なる温度で加熱され、かつ、互いに異なる圧力で加圧された少なくとも２種類の製品を用い、
    　前記少なくとも２種類の製品のそれぞれについて求められた、ボイドの個数密度、最大亀裂長さ、および／または、最大亀裂がまたがる結晶粒の数に基づいて、前記検量線を作成することを特徴とする、請求項１～８のいずれか１項に記載の検量線作成方法。     As the second product, at least two types of products heated at different temperatures and pressurized at different pressures are used,
    The calibration curve is created based on the number density of voids, the maximum crack length, and / or the number of crystal grains spanning the maximum crack, which are obtained for each of the at least two types of products. The method for preparing a calibration curve according to any one of claims 1 to 8.
  10. 　前記少なくとも２種類の製品の寿命が、最も長い製品の寿命を基準として他の製品の寿命が２５％以内の差であることを特徴とする、請求項９に記載の検量線作成方法。 10. The calibration curve creating method according to claim 9, wherein the lifetimes of the at least two types of products are different within 25% of the lifetimes of other products based on the lifetime of the longest product.
  11. 　加熱及び加圧により劣化した製品のクリープ余寿命を予測する方法であって、
    　　前記製品の表面において、任意の評価範囲を設定する工程と、
    　　前記評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、
    　　前記評価範囲内において、亀裂が生じていない場合には、
    　　　前記評価範囲内において、ボイドの個数密度を求める工程と、
    　　　得られたボイドの個数密度から前記製品の損傷率を求める工程とをさらに含み、
    　　前記評価範囲内において、亀裂が生じている場合には、
    　　　前記評価範囲内において生じた最大亀裂の長さを求める工程と、
    　　　得られた最大亀裂長さから前記製品の損傷率を求める工程とをさらに含み、
    　前記製品がベイナイト組織を有することを特徴とする、クリープ余寿命予測方法。     A method for predicting the remaining creep life of a product deteriorated by heating and pressurization,
    On the surface of the product, setting an arbitrary evaluation range;
    Determining whether or not a crack has occurred within the evaluation range,
    Within the evaluation range, if no cracks have occurred,
    Within the evaluation range, obtaining a void number density;
    And further determining the damage rate of the product from the number density of voids obtained,
    In the evaluation range, if a crack has occurred,
    A step of determining the length of the maximum crack generated within the evaluation range;
    Further determining the damage rate of the product from the obtained maximum crack length,
    The creep remaining life prediction method, wherein the product has a bainite structure.
  12. 　加熱及び加圧により劣化した製品のクリープ余寿命を予測する方法であって、
    　　前記製品の表面において、任意の評価範囲を設定する工程と、
    　　前記評価範囲内において、亀裂が生じているか否かを判定する工程とを含み、
    　　前記評価範囲内において、亀裂が生じていない場合には、
    　　　前記評価範囲内において、ボイドの個数密度を求める工程と、
    　　　得られたボイドの個数密度から前記製品の損傷率を求める工程とをさらに含み、
    　　前記評価範囲内において、亀裂が生じている場合には、
    　　　前記評価範囲内において生じた最大亀裂がまたがる結晶粒の数を求める工程と、
    　　　得られた結晶粒の数から前記製品の損傷率を求める工程とをさらに含み、
    　前記製品がベイナイト組織を有することを特徴とする、クリープ余寿命予測方法。     A method for predicting the remaining creep life of a product deteriorated by heating and pressurization,
    On the surface of the product, setting an arbitrary evaluation range;
    Determining whether or not a crack has occurred within the evaluation range,
    Within the evaluation range, if no cracks have occurred,
    Within the evaluation range, obtaining a void number density;
    And further determining the damage rate of the product from the number density of voids obtained,
    In the evaluation range, if a crack has occurred,
    Determining the number of crystal grains spanned by the maximum crack generated within the evaluation range;
    And further determining the damage rate of the product from the number of crystal grains obtained,
    The creep remaining life prediction method, wherein the product has a bainite structure.
  13. 　前記評価範囲を、前記製品の表面において亀裂が生じやすい箇所に設定することを特徴とする、請求項１１または１２に記載の検量線の作成方法。 The method for creating a calibration curve according to claim 11 or 12, wherein the evaluation range is set to a location where cracks are likely to occur on the surface of the product.
  14. 　最大亀裂が寸断されている場合に、寸断されている各箇所の長さが、その寸断箇所が隣接する両亀裂のうち長い方の長さに対して所定の割合以下であれば、最大亀裂は寸断されていないものとみなして、最大亀裂長さ、または、最大亀裂がまたがる結晶粒の数を求めることを特徴とする、請求項１１～１３のいずれか1項に記載のクリープ余寿命予測方法。 When the maximum crack is cut, if the length of each cut portion is less than a predetermined ratio with respect to the longer length of the two adjacent cracks, the maximum crack is The creep remaining life prediction method according to any one of claims 11 to 13, wherein the maximum crack length or the number of crystal grains spanning the maximum crack is obtained by assuming that the crack is not broken. .
  15. 　所定の割合が半分であることを特徴とする、請求項１４に記載のクリープ余寿命予測方法。 15. The creep remaining life prediction method according to claim 14, wherein the predetermined ratio is half.
  16. 　前記製品が中空管であることを特徴とする、請求項１１～１５のいずれか１項に記載のクリープ余寿命の予測方法。 The creep remaining life prediction method according to any one of claims 11 to 15, wherein the product is a hollow tube.
  17. 　前記製品が曲がり部分を有するボイラ用配管であることを特徴とする、請求項１６に記載のクリープ余寿命の予測方法。 The creep remaining life prediction method according to claim 16, wherein the product is a boiler pipe having a bent portion.
  18. 　前記加圧が前記製品に内圧を加えることにより行われることを特徴とする、請求項１５または１６に記載のクリープ余寿命の予測方法。 The creep remaining life prediction method according to claim 15 or 16, wherein the pressurization is performed by applying an internal pressure to the product.
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