Method and apparatus for eddy current detection of thermal damage to the substrate of parts after grinding

Abstract

This invention discloses an eddy current detection method for thermal damage to the substrate of a part after grinding. The method systematically covers the entire eddy current detection process, enabling direct detection of the substrate material under coatings / platings. It offers advantages such as being non-destructive, simple to operate, non-contact with the part during detection, and fast detection speed. This invention also provides an eddy current detection device for thermal damage to the substrate of a part after grinding.

Description

Technical Field

[0001] This invention relates to a method and apparatus for detecting eddy current damage to the substrate of a part after grinding, which belongs to the field of nondestructive testing. Background Technology

[0002] When grinding high-strength steel workpieces with chromium or tungsten carbide coatings, improper grinding parameters can easily lead to grinding burns on the surface of the substrate material. These burns can cause premature workpiece failure or reduced fatigue life, thus requiring thermal damage testing of the substrate material. The conventional method is acid etching, but this method requires removal of the coating / plating before testing and cannot be used to directly inspect workpieces with coatings / platings.

[0003] Eddy current testing, as a conventional non-destructive testing method, is well-established for detecting discontinuities such as cracks, but its application in detecting thermal damage is relatively limited. Chinese patent CN202110371263.3 discloses a method for preparing comparative specimens for acceptance criteria in eddy current testing of thermal damage. Previously, there was no scientifically authoritative method for preparing comparative specimens for thermal damage, and these specimens are essential components for debugging the testing system before eddy current testing. The paper "Eddy Current Testing of Thermal Damage from Grinding of 300M Steel" discloses the sensitivity of eddy current testing to the severity of thermal damage, aiming to demonstrate the feasibility and sensitivity of eddy current testing for thermal damage. Therefore, the aforementioned patents and papers constitute necessary foundational research for eddy current testing methods for thermal damage. Based on this, there is an urgent need to further research a feasible and systematic eddy current testing method for thermal damage on the surface of high-strength steel coated / plated substrates after grinding, in order to solve the problem of detecting grinding burns on coated / plated parts. Summary of the Invention

[0004] The present invention aims to provide a method for detecting thermal damage to the substrate of a part after grinding. The method systematically covers the entire process of thermal damage eddy current detection, realizes direct detection of the substrate material under the coating / plating layer, and has the advantages of being non-destructive, simple to operate, not in contact with the part during detection, and fast detection speed.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: an eddy current detection method for thermal damage to a substrate of a component, the detection method comprising the following steps:

[0006] Step 1) Select a material with the same material and heat treatment state as the part to be inspected to prepare a grinding burn test block; the test block includes a non-burned area, a burned area, and a grooved area, the non-burned area is located in the middle of the burned area and the grooved area, so that the signals of the burned area and the grooved area are more obvious than those of the non-burned area; process the test block using the same coating / plating process as the part to be inspected;

[0007] Step 2), fix the test block on the fixture and install the eddy current detection probe on the surface of the test block;

[0008] Step 3), start the control console of the tooling to make the test block rotate at a constant speed;

[0009] Step 4) Start the eddy current testing equipment, set and adjust the testing parameters according to the preset requirements; the eddy current testing probe moves along the axial direction of the test block and scans the unburned area, the burned area and the grooved area;

[0010] Step 5), remove the test block, clamp the part to be inspected according to step 2), repeat step 3), start the console to rotate at the same speed, keep the detection parameters in step 4), and move the eddy current detection probe along the axial direction of the part to be inspected until the surface of the part to be inspected is completely scanned.

[0011] Step 6) Record the test results and mark the suspected burn area and the confirmed burn area on the part to be inspected.

[0012] According to embodiments of the present invention, the present invention can be further optimized, and the optimized technical solution is as follows:

[0013] In one preferred embodiment, in step 1), the width of the unburned area exceeds the diameter of the eddy current detection probe.

[0014] In one preferred embodiment, in step 1), the coating / plating thickness of the test block differs from the coating / plating thickness of the part to be inspected by no more than ±30µm.

[0015] In one preferred embodiment, in step 2), the detection surface of the eddy current detection probe is 0.2 ± 0.1 mm away from the test surface of the test block;

[0016] In one preferred embodiment, the preset requirements in step 4) include: setting detection parameters such as detection frequency, gain, high / low pass, and phase angle so that the amplitude of the eddy current detection signal in the burned area exceeds 50% of the full screen height, the amplitude of the eddy current detection signal in the unburned area does not exceed 10% of the full screen height, and the eddy current detection signal in the grooved area is horizontal. The full screen height refers to the height at which the display elements of the eddy current detection signal fill the entire screen.

[0017] In one preferred embodiment, the speed of axial movement in steps 4) and 5) is no more than the effective detection width per revolution of the eddy current detection probe.

[0018] In one preferred embodiment, step 6) specifically includes:

[0019] The area without burns is defined as the eddy current detection signal amplitude of the part to be inspected does not exceed 10% of the full screen height.

[0020] The area of ​​suspected burns is defined as the eddy current detection signal amplitude of the part under inspection that is greater than 10% of the full screen height but less than 25% of the full screen height.

[0021] The burn area is determined when the amplitude of the eddy current detection signal of the part to be inspected is greater than or equal to 25% of the full screen height.

[0022] In one preferred embodiment, step 7) involves verifying the part to be inspected with suspected burn areas using the Barkhausen noise method, or verifying it using an acid etching method after removing the coating, thereby improving the grinding parameters.

[0023] Based on the same concept, the present invention also provides an apparatus for detecting thermal damage to the substrate of a component using the above-described eddy current method.

[0024] The device includes eddy current testing equipment, tooling, and eddy current testing probe;

[0025] The eddy current testing equipment includes an eddy current testing display panel and an eddy current testing control panel.

[0026] The fixture includes a control console, a clamping device, a probe holder, and a base; the clamping device is used to clamp the test block or the part to be inspected; both the clamping device and the probe holder are mounted on the base, and the probe holder can move horizontally along the base;

[0027] The eddy current detection probe is mounted on the probe fixing member. The eddy current detection probe can be adjusted up and down along the direction perpendicular to the base so that the detection surface of the eddy current detection probe is separated from the test surface of the test block or the test surface of the part to be tested by the first distance.

[0028] The eddy current detection probe and the eddy current detection control panel are electrically connected.

[0029] In one preferred embodiment, the probe holder further includes an extension rod for detecting the deep inner hole of the part to be inspected.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention enables thermal damage detection of the substrate material under the coating / plating without removing the coating / plating layer. It uses specialized tooling to clamp the part to be inspected and the eddy current detection probe, ensuring a fixed relative position between the probe and the part, avoiding excessive interference signals and making the detection signal more stable. This invention is non-destructive to the workpiece, simple and controllable in operation, provides reliable detection results, and has high detection efficiency. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the device used in Example 2;

[0033] Figure 2 This is a detection signal diagram of the unburned portion of the test block in Example 3;

[0034] Figure 3 This is a detection signal diagram of the burned areas on the test block in Example 3;

[0035] Figure 4 This is a detection signal diagram of the grooved area of ​​the test block in Example 3;

[0036] Figure 5 This is a diagram of the piston rod detection signal in Example 3.

[0037] Among them, 1. Eddy current testing equipment, 2. Tooling, 11. Eddy current testing display panel, 12. Eddy current testing control panel, 13. Eddy current testing probe, 21. Tooling control console, 22. Chuck, 23. Probe fixing component, 24. Top, 25. Limiting component, 26. Fixed base. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0039] Example 1

[0040] This embodiment provides a method for detecting thermal damage on the substrate surface of a part after grinding, the steps of which are as follows:

[0041] (i) Select the same material with the same heat treatment state as the part to be inspected to make a grinding burn test block; the test block includes a non-burned area, a burned area and a grooved area; the non-burned area is located in the middle of the burned area and the grooved area, so that the signals of the burned area and the grooved area are more obvious than those of the non-burned area; then use the same process as the part to be inspected to perform chrome plating or supersonic flame spraying;

[0042] (ii) Fix the test block on the tooling and install the eddy current detection probe on the surface of the test block;

[0043] (iii) Start the control console of the tooling to make the test block rotate at a constant speed;

[0044] (iv) Start the eddy current testing equipment, and set and adjust the testing parameters such as frequency, gain, high / low pass and phase angle according to the preset requirements; the eddy current testing probe moves along the axial direction of the test block and scans the unburned area, the burned area and the grooved area;

[0045] (V) Remove the test block, clamp the part to be inspected according to step (II), start the control console of the tooling and rotate it at the same linear speed, keep the detection parameters in step (IV), and make the eddy current detection probe move slowly along the axis of the part to be inspected until all the surfaces of the part to be inspected are scanned; the speed of the axial movement shall not exceed the effective detection width of the eddy current detection probe per revolution.

[0046] (vi) Record the test results and mark the suspected burn area and the confirmed burn area on the part to be inspected.

[0047] In steps (iv) and (v), the residual magnetism of the test block and the part to be tested does not exceed 3 Gauss.

[0048] To ensure a clearer distinction between the burned area and the grooved area in practical applications, in step (i), the width of the unburned area should exceed the diameter of the eddy current detection probe; in this embodiment, the width of the unburned area exceeds 50 mm. The grooved area, along the axial direction of the test block, has a groove width of 0.1 mm, a depth of 0.2 mm, and a length of 0.5 mm.

[0049] Furthermore, in step (i), the coating / plating thickness of the test block differs from the coating / plating thickness of the part to be inspected by no more than ±30µm.

[0050] Furthermore, in step (ii), the detection surface of the eddy current detection probe is 0.2±0.1mm away from the test surface of the test block;

[0051] Further, in step (iv), the preset requirements include: by setting detection parameters such as detection frequency, gain, high / low pass, and phase angle, ensuring that the amplitude of the eddy current detection signal in the burned area exceeds 50% of the full screen height, that the amplitude of the eddy current detection signal in the unburned area does not exceed 10% of the full screen height, and that the eddy current detection signal in the grooved area is horizontal. The full screen height refers to the height at which the display elements of the eddy current detection signal fill the entire screen.

[0052] Further, step (vi) specifically includes: the eddy current detection signal amplitude of the part under test not exceeding 10% of the full screen height is a non-burn area; the eddy current detection signal amplitude of the part under test is greater than 10% and less than 25% of the full screen height is a suspected burn area; and the eddy current detection signal amplitude of the part under test is greater than or equal to 25% of the full screen height is a confirmed burn area.

[0053] The eddy current detection signal amplitude of the burn area of ​​the test block needs to reach 50%, while the eddy current detection signal amplitude of the part to be inspected is determined to be a burn area if it reaches 25% or more, in order to ensure that no area is missed.

[0054] To further verify the method for detecting thermal damage on the surface of a part after grinding provided in this embodiment, the detection method further includes the following steps:

[0055] (vii) The parts to be inspected with suspected burn areas shall be verified by the Barkhausen noise method, or by acid etching after removing the coating. Parts with burns shall be rejected after verification, and the processing parameters of the parts shall be improved.

[0056] Example 2

[0057] This embodiment provides a device for detecting thermal damage to the substrate surface of a part after grinding. The device includes an eddy current testing device 1, a tooling 2, and an eddy current testing probe 13.

[0058] The eddy current testing device 1 includes an eddy current testing display panel 11 and an eddy current testing control panel 12;

[0059] The tooling 2 includes a control console 21, a clamping device, a probe fixing member 23, and a base 26; the clamping device is used to clamp the test block or the part to be inspected; the clamping device and the probe fixing member 23 are both mounted on the base, and the probe fixing member 23 can move horizontally along the base 26.

[0060] The eddy current detection probe 13 is mounted on the probe fixing member 23. The eddy current detection probe 13 can be adjusted up and down along the direction perpendicular to the base 26, so that the detection surface of the eddy current detection probe 13 is separated from the test surface of the test block or the test surface of the part to be inspected by the first distance.

[0061] The eddy current detection probe and the eddy current detection control panel are electrically connected.

[0062] Furthermore, the probe holder 23 also includes an extension rod for detecting the deep inner hole of the part to be inspected. When detecting the deep inner hole, the part to be inspected rotates, and the extension rod and the eddy current detection probe 13 move horizontally along the length of the base 26. Similar to the detection method for the outer cylindrical surface, the detection of the deep inner hole also requires the preparation of a comparison test block, and the detection steps are basically the same.

[0063] In this embodiment, the clamping device can clamp or clamp cylindrical parts through the tip 24 and rotate at a set speed. During clamping, the outer circular surface or the inner hole surface can be detected. The rotation speed is adjustable.

[0064] The thermal damage detection device for the substrate surface after grinding of parts provided in this embodiment can not only detect burns on the outer cylindrical surface of the part to be inspected, but also detect thermal damage on the surface of deep inner holes that are not visible to the naked eye.

[0065] Example 3

[0066] In this embodiment, there is a piston rod part to be inspected. The part is made of 300M ultra-high strength steel. The area to be inspected is the outer circular surface with a diameter of Ф180mm. The surface is chrome-plated, the length of which is 900mm. The thickness of the chrome plating after grinding is 100-110µm. The drawing requires burn testing of the base material of the ground chrome plating area.

[0067] Based on the method for detecting thermal damage to the substrate surface of a part after grinding provided in Example 1, this example detects the eddy current of thermal damage to the substrate of a 300M ultra-high strength steel coated / plated part after grinding, specifically including the following steps:

[0068] I. Preparations before parts inspection

[0069] (1) Preparation of burn comparison test blocks

[0070] A test block was prepared using 300M steel (outer diameter 180mm, inner diameter 160mm) in the same heat-treated state as the workpiece to be inspected. The test block was 300mm long. A grinding burn was created on one part of the test block, and the grinding burn was verified by acid etching. Another part of the test block had a groove along its axial direction, with a groove width of 0.1mm, a depth of 0.2mm, and a length of 0.5mm. There was a non-burned area of ​​more than 50mm between the burned area and the groove area. Chromium plating was performed using the same process as the part, with a chromium layer thickness of 100-110µm.

[0071] II. Testing Process and Results

[0072] The basic process flow of the detection method in this embodiment is as follows: demagnetize the test block, clamp the test block, start the control panel 21, turn on the eddy current detector 1, move the probe fixing part 23 to the burn area, the non-burn area and the groove area, adjust the detection parameters of the eddy current detection control panel 12 to the preset display signal, remove the test block, demagnetize the part, clamp the part, scan all the surfaces to be inspected by the eddy current detection probe 13, and the detection is completed.

[0073] (1) Adjusting test parameters using burn comparison test blocks

[0074] After demagnetizing the test block (with residual magnetism less than 3 Guass), it is clamped onto the tooling table using a clamp-and-cushion method. One end of the test block's outer diameter is held by chuck 22, and the other end is held against the inner hole by center 24. The test block is manually rotated, and the surface runout is checked and controlled within ±30µm. Surface runout refers to the change in position of a point on the surface of a part relative to the reference axis during rotation.

[0075] (2) Start the control console 21, causing the chuck 22 and the test block to rotate simultaneously at a speed of 100 R / min, where R represents 1 revolution. Turn on the eddy current detector 1 (model ELOTEST310). Move the probe holder 23 to the non-burned area, the burned area, and the grooved area respectively. Adjust the detection parameters: frequency 60kHz, gain 54dB, low pass 130Hz, high pass 8Hz, phase angle 217.5°. The preset signals are displayed at each location. The detection signal for the non-burned area of ​​the test block is as follows: Figure 2 As shown, the detection signal does not exceed 10% of the full screen height; the detection signal for areas with burns on the test block is as follows. Figure 3 As shown, the detection signal exceeds 50% of the full screen height; the detection signal in the grooved area of ​​the test block is as follows. Figure 4 As shown, the detection signal is in the horizontal direction.

[0076] (3) Remove the test block;

[0077] (4) After demagnetizing the part (with residual magnetism less than 3 Guass), clamp it on the tooling table in the same way and start testing from one end of the part with the same parameters as the test block. The part rotation speed is 100 R / min. The probe fixing part 23 moves along the axial direction to the other end on the surface of the part at a speed not exceeding 0.5D / R until the entire surface to be inspected is completely scanned. D represents the probe diameter. In this embodiment, D is 11 mm.

[0078] (5) Defect evaluation criteria: such as Figure 5 As shown, when the detected part has a defect signal amplitude greater than or equal to 25% of the full screen height, it is judged as a burn defect, the part is unqualified, and the grinding quality needs to be improved.

[0079] (6) Remove the parts and the inspection is complete.

[0080] III. Figure 1 As shown, in this embodiment, the tooling 2 includes a tooling control console 21, a chuck 22, a probe fixing component 23, a center point 24, and a limiting component 25, all located on a fixed base 26. The probe fixing component 23 and the limiting component 25 can both move horizontally along the fixed base 26. The limiting component 25 is used to limit the part to be inspected. The eddy current detection probe 13 is located on the probe fixing component 23 and can move horizontally with the probe fixing component 23. The eddy current detection probe 13 can be adjusted up and down on the probe fixing component 23 to ensure that the eddy current detection probe is always perpendicular to the surface of the part and the distance between the probe and the surface of the part is about 0.1mm to 0.3mm.

[0081] IV. The eddy current testing probe 13 is electrically connected to the eddy current testing control panel 12. The eddy current testing display panel 11 and the eddy current testing control panel 12 constitute the complete eddy current testing equipment.

[0082] 5. When inspecting the inner hole, only use the chuck 22 to clamp one end of the part, and the probe fixing member extends into the inner hole from the other end of the part in the form of an extension rod, keeping the inspection probe 13 perpendicular to the surface of the inner hole and at a distance of about 0.1mm to 0.3mm.

[0083] The method for detecting thermal damage on the substrate surface of high-strength steel after grinding of coating / plating provided in this embodiment of the invention can also be applied to the detection of uncoated / unplated surfaces. The detection does not remove any material from the surface of the part and does not affect the dimensions. Only a comparative test block with thermal damage in the same state as the part needs to be made.

[0084] In summary, the embodiments of the present invention provide a feasible method for detecting thermal damage on the substrate surface after grinding of high-strength steel coated / plated parts, which solves the problem of grinding burn detection of coated / plated parts. The detection method can directly detect the substrate material under the coating / plating and has the advantages of being non-destructive, simple to operate, not in contact with the workpiece during detection, and fast detection speed. It can also detect burn defects after grinding deep inner holes.

[0085] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present embodiments by those skilled in the art will fall within the scope defined by the appended claims.

Claims

1. A method for detecting thermal damage to a substrate of a component using eddy current detection, characterized in that, The detection method includes the following steps: Step 1) Select a material with the same material and heat treatment state as the part to be inspected to make a grinding burn test block; the test block includes a non-burned area, a burned area and a grooved area, the non-burned area is located in the middle of the burned area and the grooved area; process the test block using the same coating / plating process as the part to be inspected; Step 2), fix the test block on the fixture and install the eddy current detection probe on the surface of the test block; Step 3), start the control console of the tooling to make the test block rotate at a constant speed; Step 4), start the eddy current testing equipment, set and adjust the testing parameters according to the preset requirements; the eddy current testing probe moves along the axial direction of the test block and scans the unburned area, the burned area and the grooved area; Step 5), remove the test block, clamp the part to be inspected according to step 2), repeat step 3), start the console to rotate at the same speed, keep the detection parameters in step 4), and move the eddy current detection probe along the axial direction of the part to be inspected until the surface of the part to be inspected is completely scanned. Step 6), record the test results, and mark the suspected burn area and the confirmed burn area on the part to be inspected.

2. The eddy current detection method for thermal damage to the substrate of a part according to claim 1, characterized in that, In step 1), the width of the unburned area exceeds the diameter of the eddy current detection probe.

3. The eddy current detection method for thermal damage to the substrate of a part according to claim 1, characterized in that, In step 1), the coating / plating thickness of the test block differs from the coating / plating thickness of the part to be inspected by no more than ±30µm.

4. The eddy current detection method for thermal damage to the substrate of a part according to claim 1, characterized in that, In step 2), the detection surface of the eddy current detection probe is 0.2±0.1mm away from the test surface of the test block.

5. The eddy current detection method for thermal damage to the substrate of a part according to claim 1, characterized in that, The preset requirements in step 4) include: By setting the detection frequency, gain, high / low pass, and phase angle detection parameters, the amplitude of the eddy current detection signal in the burned area is made to exceed 50% of the full screen height, the amplitude of the eddy current detection signal in the unburned area is made to not exceed 10% of the full screen height, and the eddy current detection signal in the grooved area is made to be horizontal.

6. The eddy current detection method for thermal damage to the substrate of a part according to claim 1, characterized in that, The axial movement speed in steps 4) and 5) shall not exceed the effective detection width per revolution of the eddy current detection probe.

7. The eddy current detection method for thermal damage to the substrate of a part according to claim 1, characterized in that, Step 6) specifically includes: The area without burns is defined as the eddy current detection signal amplitude of the part to be inspected does not exceed 10% of the full screen height. The area of ​​suspected burns is defined as the eddy current detection signal amplitude of the part under inspection that is greater than 10% of the full screen height and less than 25% of the full screen height. The burn area is determined when the amplitude of the eddy current detection signal of the part to be inspected is greater than or equal to 25% of the full screen height.

8. The eddy current detection method for thermal damage to the substrate of a part according to claim 1, characterized in that, The detection method further includes the following steps: Step 7) Verify the part to be inspected with suspected burn areas using the Barkhausen noise method, or verify it by acid etching after removing the coating, and improve grinding parameters.

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