A method for measuring high-temperature bolt creep deformation

Abstract

The application discloses a kind of high-temperature bolt creep deformation measurement methods, simply summarized, including the following steps: step 1) correction is carried out to measuring micrometer;Step 2) the initial length of high-temperature bolt before operation ( L 初 ) is measured; Step 3) the original length of high-temperature bolt when converting to 0 ℃ ( L 初1 );Step 4) the length of high-temperature bolt after operation ( L 运 ) is measured;Step 5) the length of high-temperature bolt after operation when converting to 0 ℃ ( L 运h );Step 6) the absolute creep deformation amount (△L) of high-temperature bolt is calculated;Step 7) the relative creep strain (ε) of high-temperature bolt is obtained.The creep measuring point of high-temperature bolt is simple and reasonable to install, and measurement error is not easy to produce.The measurement operation is simple, fast, and the measurement result is high in precision and small in error, the creep deformation of high-temperature bolt can be accurately measured by micrometer, which is convenient for industry promotion and conducive to the development of high-temperature bolt creep supervision work.

Description

TECHNICAL FIELD

[0001] The present application relates to the creep supervision and detection of high-temperature bolts in thermal power plants, and in particular to a method for measuring the creep deformation of high-temperature bolts. BACKGROUND

[0002] High-temperature bolts are one of the important components in steam turbine equipment in thermal power plants, connecting high-temperature components such as steam turbine cylinders, main steam valves, regulating valves, and steam guide pipes, to ensure that no leakage accidents occur during the operation of the unit. The shank of the bolt bears axial tensile stress, and creep deformation will occur under high-temperature and high-pressure operating conditions. Creep rupture failure is one of the main failure modes of high-temperature bolts. Therefore, the creep supervision of high-temperature bolts is an important part of the metal technology supervision in thermal power plants.

[0003] Currently, for the creep measurement of high-temperature bolts, the power industry standard DL / T 439-2018 "Technical Guidelines for High-Temperature Fasteners in Thermal Power Plants" stipulates that the creep supervision and measurement should be performed on high-pressure inner cylinder bolts. The measurement method is to punch sample holes on the end faces of the bolt on both sides before use, and to measure the distance change between the sample holes to determine the creep deformation of the high-temperature bolt. This measurement method has two problems. First, the sample hole surface will oxidize in a high-temperature environment, and the generated oxide scale is easy to fall off, causing deformation of the sample hole and affecting the measurement of the distance between the sample holes on both sides. Second, the measuring tool commonly used for creep measurement is a micrometer, and its measuring surface is a circular plane. The sample hole is concave on the bolt end face, and its inner surface is a spherical surface. The two cannot be fitted together, and there are few high-precision measuring tools in other conventional measuring tools that can be used for the measurement of the distance between the sample holes. In view of this, in actual work, the creep measurement of high-temperature bolts is rarely carried out, and the detection personnel often feel helpless. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned deficiencies in the prior art and to provide a method for measuring the creep deformation of high-temperature bolts.

[0005] The technical solution adopted by the present application to solve the above-mentioned problems is: a method for measuring the creep deformation of high-temperature bolts, characterized in that the measurement method comprises the following steps:

[0006] Step 1: At a temperature of about 20℃, use a standard rod to calibrate the micrometer for measurement, and calculate the zero correction value of the micrometer according to the following formula:

[0007]

[0008] In the formula:

[0009] B: zero correction value of the micrometer;

[0010] b1: zero value of the micrometer before measurement, mm;

[0011] b2: the zero value of the micrometer after measurement, mm.

[0012] Step 2: Perform the creep measurement before the high-temperature bolt operation, slowly rotate the micrometer ratchet to make the measuring surface of the micrometer contact the measuring surfaces of measuring points one and three; measure three times, and the measurement results are recorded as L1, L2, and L3 respectively, and take the arithmetic mean value wherein

[0013] Step 3: Similarly, perform the creep measurement on measuring points two and four, measure three times, and the measurement results are recorded as L1', L2', and L3' respectively, and take the average value wherein The initial length of the high-temperature bolt before operation is recorded as L 初 , and

[0014]

[0015] Step 4: Convert the original length of the high-temperature bolt at 0℃ to L 初1 , and calculate according to the following formula.

[0016]

[0017] In the formula:

[0018] α p : the linear expansion coefficient of the high-temperature bolt, mm / (mm·℃);

[0019] α ck : the linear expansion coefficient of the micrometer bow, mm / (mm·℃);

[0020] t p : the surface temperature near the creep measuring point, ℃;

[0021] t ck : the temperature of the micrometer bow, ℃.

[0022] Step 5: Perform the creep measurement on the high-temperature bolt after operation, and perform the creep measurement on measuring points one and three according to step 2; measure three times, and the measurement results are recorded as L 1h , L 2h , and L 3h , and take the arithmetic mean value wherein

[0023] Step 6: Similarly, perform the creep measurement on measuring points two and four, measure three times, and the measurement results are recorded as L 1h ', L 2h ', and L 3h ', and take the average value wherein the length of the high-temperature bolt after operation is recorded as L 运 , and

[0024]

[0025] Step 7: the length of the high-temperature bolt after operation at 0℃ is recorded as L 运h , and is calculated according to the following formula.

[0026]

[0027] Step 8: the absolute creep deformation of the high-temperature bolt is calculated and recorded as ΔL, and is calculated according to the following formula.

[0028] ΔL = L 运h - L 初1

[0029] Step 9: the relative creep strain of the high-temperature bolt is calculated and recorded as ε (%), and is calculated according to the following formula.

[0030]

[0031] Further, the micrometer reading should be accurate to 0.005 mm, less than 0.0025 mm can be ignored, equal to or greater than 0.0025 mm should be advanced to 0.005 mm, less than 0.0075 mm should be reduced to 0.005 mm, equal to or greater than 0.0075 mm should be advanced to 0.010 mm.

[0032] Further, if the variation between the three readings of each creep measurement point exceeds 0.010 mm, it should be re-measured.

[0033] Further, after measuring each creep measurement point, the temperature of the bow of the micrometer and the surface temperature near the creep measurement point should be measured immediately.

[0034] Further, two creep measurement points are arranged on each side of the end surface of the high-temperature bolt, including measurement point one, measurement point two, measurement point three and measurement point four, wherein measurement point one and measurement point two are arranged on one side, and measurement point three and measurement point four are arranged on the other side; the creep measurement points are all cylindrical and are divided into upper and lower layers, the upper layer of the measurement point is made of stainless steel, and the lower layer of the measurement point is made of the same material as the bolt.

[0035] Further, the two creep measurement points on each side of the end surface of the high-temperature bolt are located at the middle position between the edge of the bolt end surface and the center hole of the bolt, and are centrally symmetrically distributed with the center hole of the bolt, and the creep measurement points on the two sides of the end surface of the high-temperature bolt are respectively on the same axis.

[0036] Compared with the prior art, the present application has the following advantages and effects: the present application can realize accurate measurement of high-temperature bolt creep deformation through a micrometer, the creep measurement points are simple and reasonable to install, measurement errors are not easy to occur, measurement operation is simple and fast, the measurement result is high in precision and small in error, the present application is convenient for industry promotion, and is conducive to the development of high-temperature bolt creep supervision work. BRIEF DESCRIPTION OF DRAWINGS

[0037] Fig. 1 is a schematic diagram of high-temperature bolt creep deformation measurement in the embodiment of the present application.

[0038] Fig. 2 is a schematic diagram of the arrangement structure of high-temperature bolt creep measurement points in the embodiment of the present application.

[0039] In the figure: measurement point one 1, measurement point two 2, measurement point three 3, measurement point four 4, end face one 5, end face two 6. DETAILED DESCRIPTION

[0040] The present application will be further described in detail below in combination with the drawings and through embodiments, and the following embodiments are an explanation of the present application and the present application is not limited to the following embodiments.

[0041] EMBODIMENT

[0042] Reference Figs. 1-2 In the embodiment, two creep measurement points (measurement point one 1 and measurement point two 2, measurement point three 3 and measurement point four 4) are arranged on each side end face of the high-temperature bolt, the creep measurement points are all cylindrical and are divided into upper and lower layers, the upper layer of the measurement point is made of stainless steel, and the lower layer of the measurement point is made of the same material as the bolt; the two creep measurement points on each side end face of the high-temperature bolt are located at the intermediate position between the edge of the bolt end face and the center hole of the bolt, and are centrally symmetrically distributed with the center hole of the bolt, and the measurement point one 1 and the measurement point three 3, and the measurement point two 2 and the measurement point four 4 are respectively on the same axis.

[0043] In the embodiment, the measurement method of high-temperature bolt creep deformation includes the following steps:

[0044] Step 1: under a temperature environment of about 20℃, a standard rod is used to correct the micrometer for measurement, and the zero correction value of the micrometer is calculated according to the following formula:

[0045]

[0046] In the formula:

[0047] B: the zero correction value of the micrometer;

[0048] b1: the zero value of the micrometer before measurement, mm;

[0049] b2: the zero value of the micrometer after measurement, mm.

[0050] Step 2: Perform the creep measurement before the high-temperature bolt operation, slowly rotate the micrometer ratchet to make the measuring surface of the micrometer contact the measuring surface of measuring point one 1 and measuring point three 3; measure three times, and the measurement results are recorded as L1, L2, L3 respectively, and the arithmetic mean value is taken wherein

[0051] Step 3: Similarly, perform the creep measurement on measuring point two 2 and measuring point four 4, measure three times, and the measurement results are recorded as L1', L2', L3' respectively, and the average value is taken wherein The initial length of the high-temperature bolt before the operation is recorded as L 初 , and

[0052] Step 4: Convert the original length of the high-temperature bolt to 0℃, recorded as L 初1 , and calculate according to the following formula.

[0053]

[0054] In the formula:

[0055] α p : linear expansion coefficient of the high-temperature bolt, mm / (mm·℃);

[0056] α ck : linear expansion coefficient of the micrometer bow, mm / (mm·℃);

[0057] t p : surface temperature near the creep measuring point, ℃;

[0058] t ck : temperature of the micrometer bow, ℃.

[0059] Step 5: Perform the creep measurement after the high-temperature bolt operation, according to step 2, perform the creep measurement on measuring point one 1 and measuring point three 3; measure three times, and the measurement results are recorded as L 1h , L 2h , L 3h , and the arithmetic mean value is taken wherein

[0060]

[0061] Step 6: Similarly, perform the creep measurement on measuring point two 2 and measuring point four 4, measure three times, and the measurement results are recorded as L 1h ', L 2h ', L 3h ', and the average value is taken wherein The length of the high-temperature bolt after the operation is recorded as L 运 , and

[0062] Step 7: convert the length of the high-temperature bolt after operation to 0℃, recorded as L 运h And calculate according to the following formula.

[0063]

[0064] Step 8: calculate the absolute creep deformation of the high-temperature bolt, recorded as ΔL, and calculate according to the following formula.

[0065] ΔL=L 运h -L 初1

[0066] Step 9: calculate the relative creep strain of the high-temperature bolt, recorded as ε (%), and calculate according to the following formula.

[0067]

[0068] In summary, the creep measuring point of the high-temperature bolt is simple and reasonable to install, and is not prone to measurement errors. The actual measurement operation is simple and fast, and is easy for detection personnel to master. The measurement result has high precision and small error. Detection personnel can accurately measure the creep deformation of the high-temperature bolt through the micrometer. The method can be popularized in the industry, and is conducive to the development of high-temperature bolt creep supervision work, and truly becomes an effective link of metal technical supervision.

[0069] The contents not described in detail in the specification all belong to the prior art known by the person skilled in the art.

[0070] Although the present application has been disclosed as above with examples, it is not intended to limit the protection scope of the present application, and any modification and decoration made by the person skilled in the art without departing from the concept and scope of the present application shall belong to the protection scope of the present application.

Claims

1. A method for measuring the creep deformation of high-temperature bolts, characterized in that, The measurement method includes the following steps: Step 1: Under a temperature environment of 20℃, use a standard bar to calibrate the measuring micrometer, and calculate the zero-point calibration value of the micrometer according to the following formula; In the formula: B: Micrometer zero-point calibration value; b1: Zero position value of the micrometer before measurement, in mm; b2: Zero value of the micrometer after measurement, in mm; Step 2: Perform creep measurement on the high-temperature bolts before operation. Slowly rotate the micrometer ratchet until the measuring surfaces of the micrometer contact the measuring surfaces of measuring points one and three. Take three measurements, and record the results as L1, L2, and L3, respectively. Take the arithmetic mean. in Step 3: Similarly, creep measurements were performed on measuring points 2 and 4, three times in total. The results were recorded as L1', L2', and L3', and the average value was taken. in The initial length of the high-temperature bolt before operation is denoted as L. 初 ,and Step 4: Convert the original length of the high-temperature bolt to 0℃, and denot it as L. 初1 , and calculate according to the following formula; In the formula: α p : Coefficient of linear expansion of high-temperature bolts, mm / (mm·℃); α ck : Coefficient of linear expansion of the micrometer bow, mm / (mm·℃); t p Surface temperature near the creep measurement point, in °C; t ck Temperature of the micrometer bow, °C; Step 5: Perform creep measurement on the high-temperature bolts after operation. Perform creep measurement at measuring points one and three as per step 2; perform three measurements, and record the results as: L 1h L 2h L 3h and take the arithmetic mean. in Step 6: Similarly, creep measurements were performed on measuring points two and four, three times, and the results were recorded as: L 1h '、L 2h '、L 3h ', and take the average value. in The length of the high-temperature bolt after operation is denoted as L. 运 ,and Step 7: Convert the length of the high-temperature bolt after operation to 0℃, and record it as L. 运h , and calculate according to the following formula; Step 8: Calculate the absolute creep deformation of the high-temperature bolt, denoted as ΔL, and calculate it according to the following formula; ΔL=L 运h -L 初1 Step 9: Calculate the relative creep strain of the high-temperature bolt, denoted as ε (%), and calculate it according to the following formula; 2. The method for measuring the creep deformation of high-temperature bolts according to claim 1, characterized in that, Micrometer readings are accurate to 0.005mm. Readings less than 0.0025mm are omitted. Readings equal to or greater than 0.0025mm are rounded up to 0.005mm. Readings less than 0.0075mm are rounded down to 0.005mm. Readings equal to or greater than 0.0075mm are rounded up to 0.010mm.

3. The method for measuring the creep deformation of high-temperature bolts according to claim 1, characterized in that, If the variation between three readings at each creep measurement point exceeds 0.010 mm, the measurement should be repeated.

4. The method for measuring the creep deformation of high-temperature bolts according to claim 1, characterized in that, After each creep measurement point is measured, the bow temperature of the micrometer and the surface temperature near the creep measurement point are immediately measured.

5. The method for measuring the creep deformation of high-temperature bolts according to claim 1, characterized in that, Two creep testing points are set on each of the two end faces of the high-temperature bolt, including testing point one, testing point two, testing point three and testing point four. Testing points one and two are set on one side, and testing points three and four are set on the other side. The creep testing points are all cylindrical and are divided into upper and lower layers. The upper layer of the testing point is made of stainless steel, and the lower layer of the testing point is made of the same material as the bolt.

6. The method for measuring the creep deformation of high-temperature bolts according to claim 5, characterized in that, The two creep measurement points on each side of the high-temperature bolt are located in the middle between the edge of the bolt end face and the bolt center hole, and are centrally symmetrical with the bolt center hole. The creep measurement points on both sides of the high-temperature bolt are on the same axis.

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