Method for detecting shot blasting layer on inner wall of austenite heat-resistant steel pipe

Abstract

The invention discloses a method for detecting a shot blasting layer on the inner wall of an austenite heat-resistant steel pipe, which comprises the following steps of: 1, connecting an interface end of a connecting line with an interface end of a relative permeability measuring instrument host, starting up and calibrating equipment; 2, attaching the probe to a plurality of positions of the outer wall of the steel pipe, recording relative permeability values displayed on an instrument host interface, averaging to obtain A, similarly obtaining a relative permeability average value B of the inner wall of the steel pipe, and judging whether the inner wall is subjected to shot blasting treatment according to the value of B-A; 3, the probe is tightly attached to the inner wall of the steel pipe and moves slowly in the circumferential direction and the axial direction for scanning, the relative permeability C displayed on a host interface is observed, and whether a leakage spraying area exists or not is judged according to the numerical value of C-A. According to the method for detecting the shot blasting layer on the inner wall of the austenite heat-resistant steel pipe, the problem that the detection result of a missed blasting area is not accurate enough in the prior art is solved.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology, specifically relating to a method for detecting shot peening layer on the inner wall of austenitic heat-resistant steel pipe. Background Technology

[0002] As power generation equipment develops towards larger capacities, the steam temperature and operating pressure parameters of generating units are constantly increasing, placing higher demands on the high-temperature steam oxidation resistance of metallic materials used in thermal power units. Shot peening of the inner wall of austenitic heat-resistant steel pipes compresses, breaks down, and refines the surface grains. Under high-temperature operation, this promotes the diffusion of Cr atoms from the material matrix to the surface, forming a dense protective layer and significantly improving the steam oxidation resistance of the inner wall of the austenitic heat-resistant steel pipe. This method is low-cost, simple, and effective, and has been widely studied and used.

[0003] Currently, the relevant standard in the power industry, "Technical Conditions for Quality Inspection and Acceptance of Shot Peening Layer on the Inner Wall of Austenitic Heat-Resistant Steel Boiler Tubes" (DL / T 1603-2016), stipulates that visual inspection should be used for qualitative analysis of the shot peening layer. However, this method is not intuitive enough and has a low detection rate. Metallographic or microhardness methods can be used for qualitative and quantitative analysis of the shot peening layer, but these methods are complex and have low inspection efficiency. Both of these methods are not accurate enough for detecting areas where shot peening has been missed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for detecting shot peening layer on the inner wall of austenitic heat-resistant steel pipes, which solves the problem that the existing technology is not accurate enough in detecting shot peening leakage areas in steel pipes.

[0005] The technical solution adopted in this invention is a method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe, comprising the following steps: Step 1: Connect the interface end of the connecting cable to the interface end of the relative permeability measuring instrument host, turn on the power and calibrate the device; Step 2: Place the probe close to multiple locations on the outer wall of the steel pipe, record the relative permeability values ​​displayed on the instrument host interface, and take the average value to obtain A. Similarly, obtain the average relative permeability B of the inner wall of the steel pipe. Determine whether the inner wall has been shot peened based on the value of B - A. Step 3: Slowly move the probe along the circumferential and axial directions, close to the inner wall of the steel pipe, and observe the relative permeability C displayed on the host interface. Determine whether there is a leak zone based on the value of C - A.

[0006] The invention is further characterized by: The specific calibration process in step 1 is as follows: place the probe of the connecting wire in contact with the center of the test block, press the button on the main unit display screen, then move the probe away from the test block and press the button on the main unit display screen again.

[0007] When calibrating by contacting the probe of the connecting wire with the center of the test block, the probe of the connecting wire should be in perpendicular contact with the center of the test block.

[0008] The specific process for determining whether the inner wall has been shot peened in step 2 is as follows: if B - A ≤ 0.002, then the inner wall is considered not to have been shot peened; if B - A > 0.002, then the inner wall is considered to have been shot peened.

[0009] The specific process for determining whether there is a missed shot peening area in step 3 is as follows: if C - A > 0.002, then the position is considered to be a normal shot peening area; if C - A ≤ 0.002, then the position is considered to have a missed shot peening area.

[0010] When obtaining the average relative permeability A of the outer wall and the average relative permeability B of the inner wall of the steel pipe, the relative permeability at at least four different locations is measured and averaged.

[0011] When scanning the inner wall of austenitic heat-resistant steel pipes, the probe should be moved slowly and evenly to ensure the accuracy of the test results.

[0012] The main unit of the relative permeability measuring instrument is equipped with a display screen that shows the relative permeability value in real time, making it easy for operators to read and judge.

[0013] The beneficial effects of this invention are: The shot peening layer detection method for the inner wall of austenitic heat-resistant steel pipe provided by this invention is simple and safe. Compared with visual methods, it can quantify the qualitative analysis of the shot peening layer and the detection of missed areas by using a relative permeability measuring instrument. It has low requirements for the quality and experience of the testing personnel and a low probability of misjudgment and missed detection. Compared with metallographic and microhardness methods, it has higher detection efficiency and can realize the qualitative analysis of the shot peening layer on the inner wall of austenitic heat-resistant steel pipe and the detection of missed areas without cutting the pipe for sampling. At the same time, it improves the accuracy of the detection results of missed areas. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the shot peening layer detection method for the inner wall of austenitic heat-resistant steel pipe according to the present invention. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0016] Example 1 The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe proposed in this embodiment includes the following steps: Step 1: Connect the interface end of the connecting cable to the interface end of the relative permeability measuring instrument host, turn on the power and calibrate the device; Step 2: Place the probe close to multiple locations on the outer wall of the steel pipe, record the relative permeability values ​​displayed on the instrument host interface, and take the average value to obtain A. Similarly, obtain the average relative permeability B of the inner wall of the steel pipe. Determine whether the inner wall has been shot peened based on the value of B - A. Step 3: Slowly move the probe along the circumferential and axial directions, close to the inner wall of the steel pipe, and observe the relative permeability C displayed on the host interface. Determine whether there is a leak zone based on the value of C - A.

[0017] Example 2 The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe proposed in this embodiment includes the following steps: Step 1: Connect the interface end of the connecting cable to the interface end of the relative permeability measuring instrument host, turn on the power and calibrate the device; The specific calibration process is as follows: Place the probe of the connecting cable in contact with the center of the test block, press the button on the main unit display screen, then move the probe away from the test block and press the button on the main unit display screen again; When calibrating by contacting the probe of the connecting wire with the center of the test block, the probe of the connecting wire should be in perpendicular contact with the center of the test block. Step 2: Place the probe close to multiple locations on the outer wall of the steel pipe, record the relative permeability values ​​displayed on the instrument host interface, and take the average value to obtain A. Similarly, obtain the average relative permeability B of the inner wall of the steel pipe. Determine whether the inner wall has been shot peened based on the value of B - A. Step 3: Slowly move the probe along the circumferential and axial directions, close to the inner wall of the steel pipe, and observe the relative permeability C displayed on the host interface. Determine whether there is a leak zone based on the value of C - A.

[0018] Example 3 The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe proposed in this embodiment includes the following steps: Step 1: Connect the interface end of the connecting cable to the interface end of the relative permeability measuring instrument host, turn on the power and calibrate the device; The specific calibration process is as follows: Place the probe of the connecting cable in contact with the center of the test block, press the button on the main unit display screen, then move the probe away from the test block and press the button on the main unit display screen again; When calibrating by contacting the probe of the connecting wire with the center of the test block, the probe of the connecting wire should be in perpendicular contact with the center of the test block. Step 2: Place the probe close to multiple locations on the outer wall of the steel pipe, record the relative permeability values ​​displayed on the instrument host interface, and take the average value to obtain A. Similarly, obtain the average relative permeability B of the inner wall of the steel pipe. Determine whether the inner wall has been shot peened based on the value of B - A. The specific process for determining whether the inner wall has been shot peened is as follows: if B - A ≤ 0.002, then the inner wall is considered not to have been shot peened; if B - A > 0.002, then the inner wall is considered to have been shot peened. Step 3: Slowly move the probe along the circumferential and axial directions, close to the inner wall of the steel pipe, and observe the relative permeability C displayed on the host interface. Determine whether there is a leak zone based on the value of C - A.

[0019] Example 4 The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe proposed in this embodiment is as follows: Figure 1 As shown, it includes the following steps: Step 1: Connect the interface end of the connecting cable to the interface end of the relative permeability measuring instrument host, turn on the power and calibrate the device; The main unit of the relative permeability measuring instrument is equipped with a display screen that shows the relative permeability value in real time, making it easy for operators to read and judge. The specific calibration process is as follows: Place the probe of the connecting cable in contact with the center of the test block, press the button on the main unit display screen, then move the probe away from the test block and press the button on the main unit display screen again; When calibrating by contacting the probe of the connecting wire with the center of the test block, the probe of the connecting wire should be in perpendicular contact with the center of the test block. Step 2: Place the probe close to multiple locations on the outer wall of the steel pipe, record the relative permeability values ​​displayed on the instrument host interface, and take the average value to obtain A. Similarly, obtain the average relative permeability B of the inner wall of the steel pipe. Determine whether the inner wall has been shot peened based on the value of B - A. The specific process for determining whether the inner wall has been shot peened is as follows: if B - A ≤ 0.002, then the inner wall is considered not to have been shot peened; if B - A > 0.002, then the inner wall is considered to have been shot peened. When obtaining the average relative permeability A of the outer wall and the average relative permeability B of the inner wall of the steel pipe, the relative permeability at at least four different locations is measured and averaged. Step 3: Slowly move the probe along the circumferential and axial directions close to the inner wall of the steel pipe to scan and observe the relative permeability C displayed on the host interface. Determine whether there is a leak area based on the value of C - A. The specific process for determining whether there is a missed shot peening area is as follows: if C - A > 0.002, then the location is considered a normal shot peening area; if C - A ≤ 0.002, then the location is considered to have a missed shot peening area. When scanning the inner wall of austenitic heat-resistant steel pipes, the probe should be moved slowly and evenly to ensure the accuracy of the test results.

[0020] Example 5 The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe proposed in this embodiment is as follows: Figure 1 As shown, it includes the following steps: Taking austenitic heat-resistant steel pipe of Super304 material as an example, the qualitative analysis of the shot-peened layer is explained in detail: First, place the probe close to the outer wall of the steel pipe at position 1. The instrument main interface displays the relative permeability value as a1. The relative permeability of the outer wall of the steel pipe at positions 2, 3, and 4 is obtained using the same method, as shown in Table 1. The average value of the four values ​​is taken as A. Next, place the probe close to the inner wall of the steel pipe at position 1. The instrument main interface displays the relative permeability as b1. The relative permeability of the inner wall of the steel pipe at positions 2, 3, and 4 is obtained using the same method, as shown in Table 1. The average value of the four values ​​is taken as B. If B - A ≤ 0.002, it is considered that the inner wall of the austenitic heat-resistant steel of Super304 material has not been shot-peened; if B - A > 0.002, it is considered that its inner wall has been shot-peened.

[0021] Table 1. Relative permeability of the inner and outer walls of Super304

[0022] The following is a detailed explanation based on experimental data: The probe was placed close to positions 1-4 on the outer wall of a Super304 austenitic heat-resistant steel pipe (inner wall shot peening). The relative permeability of the outer wall is shown in Table 2, and the average of the four values ​​was A1 = 1.00375. The same method was used to obtain the relative permeability of the inner wall at positions 1-4, as shown in Table 2, and the average of the four values ​​was B1 = 1.01025. B1 - A1 = 1.01025 - 1.00375 = 0.0065 > 0.002, indicating that the inner wall has undergone shot peening. Using austenitic heat-resistant steel pipes of different Super304 materials (inner wall shot peening), the same method was used to obtain the average relative permeability of the outer wall (A2-A6) and the average relative permeability of the inner wall (B2-B6), as shown in Table 2. The values ​​of B2-A2, B3-A3, B4-A4, B5-A5, and B6-A6 are all greater than 0.002.

[0023] Table 2. Relative magnetic permeability of inner and outer walls of Super304 (internal wall shot peening)

[0024] The probe was placed close to positions 1-4 on the outer wall of a Super304 austenitic heat-resistant steel pipe (without shot peening on the inner wall). The relative permeability of the outer wall is shown in Table 3, and the average of the four values ​​was A1 = 1.0035. The same method was used to obtain the relative permeability of positions 1-4 on the inner wall, as shown in Table 3, and the average of the four values ​​was B1 = 1.00425. B1 - A1 = 1.00425 - 1.0035 = 0.00075 < 0.002, indicating that the inner wall had not undergone shot peening. Using different Super304 austenitic heat-resistant steel pipes (without shot peening on the inner wall), the average relative permeability of the outer wall (A2-A6) and the average relative permeability of the inner wall (B2-B6) were obtained using the same method, as shown in Table 3. The values ​​of B2-A2, B3-A3, B4-A4, B5-A5, and B6-A6 are all less than 0.002.

[0025] Table 3. Relative magnetic permeability of inner and outer walls of Super304 (inner wall not shot peened)

[0026] Taking a shot-peened tube sample of an austenitic heat-resistant steel pipe made of Super304 material as an example, the specific method for detecting its missed shot-peening area is explained as follows: First, place the probe close to position 1 on the outer wall of the steel pipe. The instrument host interface displays a relative permeability value of a1. The relative permeability of the outer wall of the steel pipe at positions 2, 3, and 4 is obtained using the same method, as shown in Table 1. The average value A of the four values ​​is taken. Slowly move the probe along the circumferential and axial directions, close to the inner wall of the steel pipe, and simultaneously observe the relative permeability C displayed on the host interface. If C—A>0.002, the position is considered a normal shot-peened area. If C—A≤0.002, the position is considered to have missed shot-peening.

[0027] Specific explanation based on experimental data: The probe was placed close to positions 1-4 on the outer wall of a Super304 austenitic heat-resistant steel pipe (with a leak area on the inner wall). The relative permeability is shown in Table 4, and the average of the four values ​​was taken as A=1.00375. The probe was slowly moved along the circumferential and axial directions while closely adhering to the inner wall of the steel pipe to perform scanning, and the relative permeability C1 displayed on the main unit interface was observed. The relative permeability of the normal shot peening zone is C1=1.010, C1—A=1.010—1.00375=0.00625>0.002. The relative permeability C2~C6 of other normal shot peening zones were obtained using the same method, as shown in Table 4. The values ​​of C2—A, C3—A, C4—A, C5—A, and C6—A are all greater than 0.002. The relative permeability of the missed shot peening zone is C1=1.004, C1—A=1.004—1.00375=0.00025<0.002. The relative permeability C2~C6 of other missed shot peening zones were obtained using the same method, as shown in Table 4. The values ​​of C2—A, C3—A, C4—A, C5—A, and C6—A are all less than 0.002.

[0028] Table 4. Relative magnetic permeability of inner and outer walls of Super304 (with leaked areas on the inner wall)

[0029] Example 6 The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe proposed in this embodiment is as follows: Figure 1 As shown, it includes the following steps: Taking TP347HFG austenitic heat-resistant steel pipe as an example, the qualitative analysis of the shot-peened layer is explained in detail: First, place the probe close to position 1 on the outer wall of the steel pipe. The instrument main interface displays the relative permeability value as d1. Using the same method, obtain the relative permeability of the outer wall of the steel pipe at positions 2, 3, and 4, as shown in Table 5. Take the average of the four values, D. Next, place the probe close to the shot-peened layer at position 1 on the inner wall of the steel pipe. The instrument main interface displays the relative permeability as e1. Using the same method, obtain the relative permeability of the shot-peened layer of the inner wall of the steel pipe at positions 2, 3, and 4, as shown in Table 5. Take the average of the four values, E. If E - D ≤ 0.002, it is considered that the inner wall of the TP347HFG austenitic heat-resistant steel has not been shot-peened; if E - D > 0.002, it is considered that its inner wall has been shot-peened.

[0030] Table 5 Relative permeability of inner and outer walls of TP347HFG

[0031] The following is a detailed explanation based on experimental data: The probe was placed close to positions 1-4 on the outer wall of a TP347HFG austenitic heat-resistant steel pipe (inner wall shot peening). The relative permeability of the outer wall is shown in Table 6, and the average of the four values ​​was D1 = 1.004. Using the same method, the relative permeability of the inner wall at positions 1-4 was obtained, and the average of the four values ​​was E1 = 1.019. E1 - D1 = 1.019 - 1.004 = 0.015 > 0.002, indicating that the inner wall has undergone shot peening. Using austenitic heat-resistant steel pipes of different TP347HFG materials (inner wall shot peening), the average relative permeability of the outer wall (D2-D6) and the average relative permeability of the inner wall (E2-E6) were obtained using the same method, as shown in Table 6. The values ​​of E2-D2, E3-D3, E4-D4, E5-D5, and E6-D6 are all greater than 0.002.

[0032] Table 6. Relative magnetic permeability of inner and outer walls of TP347HFG (inner wall shot peening)

[0033] The probe was placed close to positions 1-4 on the outer wall of a TP347HFG austenitic heat-resistant steel pipe (without shot peening on the inner wall). The relative permeability of the outer wall is shown in Table 7, and the average of the four values ​​was D1 = 1.0035. The same method was used to obtain the relative permeability of positions 1-4 on the inner wall, as shown in Table 7, and the average of the four values ​​was E1 = 1.004. E1 - D1 = 1.004 - 1.0035 = 0.0005 < 0.002, indicating that the inner wall had not undergone shot peening. Using austenitic heat-resistant steel pipes of different TP347HFG materials (without shot peening on the inner wall), the average relative permeability of the outer wall (D2-D6) and the average relative permeability of the inner wall (E2-E6) were obtained using the same method, as shown in Table 7. The values ​​of E2-D2, E3-D3, E4-D4, E5-D5, and E6-D6 are all less than 0.002.

[0034] Table 7. Relative magnetic permeability of inner and outer walls of TP347HFG (without shot peening)

[0035] Taking a TP347HFG austenitic heat-resistant steel pipe inner wall shot-peened sample as an example, the following is a detailed explanation of how to detect missed shot peening areas: First, place the probe close to position 1 on the outer wall of the steel pipe. The instrument host interface displays the relative permeability value as d1. Using the same method, obtain the relative permeability of the outer wall of the steel pipe at positions 2, 3, and 4, as shown in Table 5. Take the average value D of the four values. Slowly move the probe along the circumferential and axial directions, close to the inner wall of the steel pipe, and simultaneously observe the relative permeability C displayed on the host interface. If C - D ≤ 0.002, it is considered that there is a missed shot peening at that position.

[0036] Specific explanation based on experimental data: The probe was placed close to positions 1-4 on the outer wall of a TP347HFG austenitic heat-resistant steel pipe (with a leak area on the inner wall). The relative permeability is shown in Table 8, and the average of the four values ​​was taken as D=1.00375. The probe was slowly moved along the circumferential and axial directions while closely adhering to the inner wall of the steel pipe to perform scanning, while the relative permeability C1 displayed on the main unit interface was observed. The relative permeability of the normal shot peening zone is shown in Table 8: C1=1.017, C1-D=1.017-1.00375=0.01325>0.002. The relative permeability C2~C6 of other normal shot peening zones were obtained using the same method, as shown in Table 8. The values ​​of C2-D, C3-D, C4-D, C5-D, and C6-D are all greater than 0.002. The relative permeability of the missed shot peening zone is shown in Table 8: C1=1.005, C1-D=1.005-1.00375=0.00125<0.002. The relative permeability C2~C6 of other missed shot peening zones were obtained using the same method, as shown in Table 8. The values ​​of C2-D, C3-D, C4-D, C5-D, and C6-D are all less than 0.002.

[0037] Table 8. Relative permeability of inner and outer walls of TP347HFG (with leaked areas on the inner wall).

[0038] Compared to visual inspection, this method can quantify the qualitative analysis of the shot-peened layer on the inner wall of austenitic heat-resistant steel pipe and the detection of missed areas using a relative permeability measuring instrument. It requires less skill and experience from the inspectors and has a lower probability of misjudgment or missed detection. Compared to metallographic and microhardness methods, it is more efficient, enabling qualitative analysis of the shot-peened layer on the inner wall of austenitic heat-resistant steel pipe and detection of missed areas without the need for pipe cutting and sampling. It also improves the accuracy of the results for detecting missed areas.

Claims

1. A method for detecting shot peening layer on the inner wall of austenitic heat-resistant steel pipe, characterized in that, Includes the following steps: Step 1: Connect the interface end of the connecting cable to the interface end of the relative permeability measuring instrument host, turn on the power and calibrate the device; Step 2: Place the probe close to multiple locations on the outer wall of the steel pipe, record the relative permeability values ​​displayed on the instrument host interface, and take the average value to obtain A. Similarly, obtain the average relative permeability B of the inner wall of the steel pipe. Determine whether the inner wall has been shot peened based on the value of B - A. Step 3: Slowly move the probe along the circumferential and axial directions, close to the inner wall of the steel pipe, and observe the relative permeability C displayed on the host interface. Determine whether there is a leak zone based on the value of C - A.

2. The method for detecting shot peening layer on the inner wall of austenitic heat-resistant steel pipe according to claim 1, characterized in that, The specific calibration process described in step 1 is as follows: Place the probe of the connecting wire in contact with the center of the test block, press the button on the main unit display screen, then move the probe away from the test block and press the button on the main unit display screen again.

3. The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe according to claim 2, characterized in that, When calibrating the connection by placing the probe of the connecting wire in contact with the center of the test block, the probe of the connecting wire is in perpendicular contact with the center of the test block.

4. The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe according to claim 1, characterized in that, The specific process for determining whether the inner wall has been shot peened in step 2 is as follows: if B - A ≤ 0.002, the inner wall is considered not to have been shot peened; if B - A > 0.002, the inner wall is considered to have been shot peened.

5. The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe according to claim 1, characterized in that, The specific process for determining whether there is a missed shot peening area in step 3 is as follows: if C - A > 0.002, then the position is considered to be a normal shot peening area; if C - A ≤ 0.002, then the position is considered to have missed shot peening.

6. The method for detecting shot peening layer on the inner wall of austenitic heat-resistant steel pipe according to claim 1, characterized in that, When obtaining the average relative permeability A of the outer wall and the average relative permeability B of the inner wall of the steel pipe, the relative permeability at at least four different locations is measured and averaged.

7. The method for detecting the shot peening layer on the inner wall of austenitic heat-resistant steel pipe according to claim 1, characterized in that, When scanning the inner wall of austenitic heat-resistant steel pipes, the probe should be moved slowly and evenly to ensure the accuracy of the test results.

8. The method for detecting shot peening layer on the inner wall of austenitic heat-resistant steel pipe according to claim 1, characterized in that, The main unit of the relative permeability measuring instrument is equipped with a display screen that displays the relative permeability value in real time, making it easy for operators to read and judge.

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