Method and device for detecting internal defects of metal sample

Abstract

The invention belongs to the technical field of metal detection, and discloses a method and a device for detecting internal defects of a metal sample, and the method comprises the following steps: cutting a metal piece with internal defects to obtain the metal sample; forming a detection groove parallel to the internal defect in the surface of the metal sample; performing liquid nitrogen treatment on the metal sample with the detection groove; after liquid nitrogen treatment, pressure is applied to the surface of the metal sample, so that the metal sample is broken along the detection groove, and internal defects are exposed; and analyzing the exposed internal defects of the metal sample. According to the method, the metal sample is cut with the internal defect as the center, the detection groove corresponding to the internal defect is formed in the surface of the sample, and then pressure is applied to the metal sample to break the metal sample, so that the internal defect at the broken position is detected, and the method has important significance.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal detection, and particularly relates to a method and device for detecting internal defects of a metal specimen. Background Art

[0002] In the engineering applications of oil pipes and other metal materials, various tiny cracks and other defects are inevitably generated inside and on the surface of the products during the preparation, processing, and use processes. If the cracks or defects further expand, the strength, toughness, and service life of the materials will be reduced, and even the products will eventually fail and be damaged. Therefore, the method of opening and studying the internal defects or cracks of the samples is of extremely important significance. Summary of the Invention

[0003] In order to solve at least one problem in the background art, the present invention provides a method and device for detecting internal defects of a metal specimen.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for detecting internal defects of a metal specimen includes the following steps:

[0006] Cut a metal piece with internal defects to obtain a metal specimen;

[0007] Open a detection groove parallel to the internal defect on the surface of the metal specimen;

[0008] Perform liquid nitrogen treatment on the metal specimen with the detection groove opened;

[0009] After the liquid nitrogen treatment, apply pressure to the surface of the metal specimen to break the metal specimen along the detection groove, exposing the internal defect;

[0010] Analyze the internal defect exposed on the metal specimen.

[0011] Preferably, cutting a metal piece with internal defects to obtain a metal specimen includes the following steps:

[0012] Detect the position of the internal defect in the metal piece;

[0013] Cut the metal piece with the position of the internal defect as the center to obtain a metal specimen in a rectangular block structure, and the internal defect is located at the center of the metal specimen.

[0014] Preferably, opening a detection groove parallel to the internal defect on the surface of the metal specimen includes:

[0015] Open a V-shaped detection groove on the surface of the metal specimen in a rectangular block structure. The detection groove extends from one end of the metal specimen to the other end, with a depth of 3 mm to 5 mm and is located in the middle of the surface of the metal specimen.

[0016] Preferably, the metal specimen with the detection groove is treated with liquid nitrogen, including:

[0017] Put the metal specimen into liquid nitrogen at -196°C to -210°C and freeze it for ten minutes.

[0018] Preferably, apply pressure to the surface of the metal specimen (1) to break the metal specimen (1) along the detection groove (3) to expose internal defects, including the following steps:

[0019] Place the metal specimen taken out of the liquid nitrogen on the tooling with the detection groove facing down;

[0020] Apply pressure to the metal specimen through the indenter of the press until the metal specimen breaks along the detection groove to expose internal defects.

[0021] Preferably, when the indenter of the press applies pressure, the descending speed > 2 mm / s.

[0022] Preferably, the time period from taking the metal specimen out of the liquid nitrogen to the metal specimen breaking along the detection groove is less than minutes.

[0023] A detection device for internal defects of a metal specimen, used for the above-mentioned method for detecting internal defects of a metal specimen, includes tooling and a press;

[0024] The tooling includes a support plate and a bottom plate. There are two bottom plates, which are parallel to each other and are installed on the surface of the bottom plate through fastening screws for supporting the metal specimen;

[0025] The bottom plate is placed under the press;

[0026] The press is equipped with an indenter, and the pressure is used to apply pressure to the surface of the metal specimen.

[0027] Preferably, a chute is opened on the bottom surface of the bottom plate, a locking groove is opened on the bottom surface of the chute, the stud of the fastening screw passes through the locking groove and is threadedly connected to the support plate, and the inner diameter of the nut of the fastening screw is greater than the width of the locking groove;

[0028] The chute is parallel to the locking groove and perpendicular to the support plate.

[0029] Preferably, when the support plate supports the metal specimen, the detection groove of the metal specimen is parallel to the support plate and is located between the two support plates.

[0030] Advantages of the present invention:

[0031] 1. The method of the present invention cuts a metal specimen centered on an internal defect, opens a detection groove corresponding to the internal defect on the surface of the specimen, and then applies pressure to the metal specimen to break it, so as to detect the internal defect at the fracture, which is of great significance;

[0032] 2. The device of the present invention proposes a tooling for placing a metal specimen. This tooling can adjust the relative distance of the support plates in the tooling according to the size of the metal specimen, and is suitable for placing metal specimens of various different specifications.

[0033] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained by the structures pointed out in the specification and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 Shows a flowchart of a method for detecting internal defects of a metal specimen of the present invention;

[0036] Figure 2 Shows a structural diagram of the metal specimen of the present invention;

[0037] Figure 3 Shows a three-dimensional structural diagram of the tooling of the present invention;

[0038] Figure 4 Shows a bottom view of the tooling of the present invention;

[0039] Figure 5 Shows a structural schematic diagram of a device for detecting internal defects of a metal specimen of the present invention.

[0040] In the figure: 1. Metal specimen; 2. Internal defect; 3. Detection groove; 4. Support plate; 5. Bottom plate; 6. Slide groove; 7. Locking groove; 8. Fastening screw; 9. Press; 10. Press head. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] Embodiment 1

[0043] A method for detecting internal defects in a metal specimen, as Figure 1 shown, includes the following steps:

[0044] S1: Cut a metal piece with an internal defect 2 to obtain a metal specimen 1; S2: Open a detection groove 3 parallel to the internal defect 2 on the surface of the metal specimen 1; S3: Perform liquid nitrogen treatment on the metal specimen 1 with the detection groove 3 opened; S4: After the liquid nitrogen treatment, apply pressure to the surface of the metal specimen 1 to cause the metal specimen 1 to break along the detection groove 3, exposing the internal defect 2; S5: Analyze the exposed internal defect 2 of the metal specimen 1.

[0045] It should be noted that in S5, in-depth analysis such as energy spectrum and scanning electron microscopy is performed on the corrosion products and fracture morphology at the fracture of the metal specimen 1 to find the cause of sample failure. Since the metal specimen 1 undergoes rapid brittle fracture at low temperature, the fracture is smooth and neat, thus ensuring that the defect part is not damaged and its shape is complete. Most of the metal specimens 1 have passed the ductile-brittle transition temperature under liquid nitrogen at -196°C to -210°C and will show brittle fracture under pressure.

[0046] Further, in S1, it specifically includes the following steps:

[0047] S101: Detect the position of the internal defect 2 in the metal piece; S102: Cut the metal piece with the position of the internal defect 2 as the center to obtain a metal specimen 1 in the shape of a rectangular block, and the internal defect 2 is located at the center of the metal specimen 1.

[0048] It should be noted that in S1, a wire cutting machine is generally used to cut the metal piece. In this embodiment, the metal specimen 1 is cut into a rectangular block structure for the convenience of detecting the metal specimen 1. Of course, the shape of the metal specimen 1 is not limited to the rectangular block structure and can also be cut into a columnar structure, etc.

[0049] It should be further noted that the internal defect 2 of the metal piece can be detected by a metal flaw detector or by using equipment such as ultrasonic waves.

[0050] Further, in combination with Figure 2It can be known that in S2, it includes: a V-shaped detection groove 3 is opened on the surface of the metal specimen 1 with a rectangular block structure. The detection groove 3 extends from one end of the metal specimen 1 to the other end, with a depth of 3 mm to 5 mm, and is located in the middle of the surface of the metal specimen 1.

[0051] Further, in S3, it includes: putting the metal specimen 1 into liquid nitrogen at -196 °C for freezing and keeping warm for ten minutes.

[0052] Further, in S4, it specifically includes the following steps:

[0053] S401: Place the metal specimen 1 taken out from the liquid nitrogen on the tooling with the detection groove 3 facing downwards; S402: Apply pressure to the metal specimen 1 through the indenter 10 of the press 9 until the metal specimen 1 breaks along the detection groove 3, exposing the internal defect 2. When the indenter 10 of the press 9 applies pressure, the descending speed > 2 mm / s. In addition, the time period from taking out the metal specimen 1 from the liquid nitrogen to the metal specimen 1 breaking along the detection groove 3 is less than 2 minutes.

[0054] Embodiment 2

[0055] For the method in Embodiment 1, as Figure 3 shown, the present invention also proposes a detection device for internal defects of a metal specimen, which is used to apply pressure to the surface of the metal specimen 1 to make the metal specimen 1 break along the detection groove 3, exposing the internal defect 2, and includes a tooling and a press 9. The tooling includes a support plate 4 and a bottom plate 5. There are two bottom plates 5, which are parallel to each other and are installed on the surface of the bottom plate 5 through fastening screws 8 for supporting the metal specimen 1; combined with Figure 5 it can be known that the bottom plate 5 is placed below the press 9; the press 9 is equipped with an indenter 10, and the indenter 10 is used to apply pressure to the surface of the metal specimen 1.

[0056] Further, a sliding groove 6 is opened on the bottom surface of the bottom plate 5, a locking groove 7 is opened on the bottom surface of the sliding groove 6, the stud of the fastening screw 8 passes through the locking groove 7 and is threadedly connected to the support plate 4, and the inscribed circle diameter of the nut of the fastening screw 8 is greater than the width of the locking groove 7. The sliding groove 6 is parallel to the locking groove 7 and perpendicular to the support plate 4. When the support plate 4 supports the metal specimen 1, the detection groove 3 of the metal specimen 1 is parallel to the support plate 4 and is located between the two support plates 4.

[0057] It should be noted that in Embodiment 2, the support plate 4 can be disassembled, then the relative distance between the two support plates 4 can be adjusted, and finally the two support plates 4 are fixed through the fastening screws 8. In addition, as Figure 4 shown, the locking groove 7 is strip-shaped, and when adjusting the relative position of the support plate 4, the fastening screw 8 can move along the locking groove 7 to the corresponding position.

[0058] The following details the method in Embodiment 1 in combination with Embodiment 2:

[0059] First, place the tooling on the platform. At the same time, adjust the distance between the support plates 4 according to the size of the metal specimen 1 and fix it with the fastening screw 8. The press 9 needs to be installed with a semi-circular indenter 10 having a crankshaft diameter of <20 mm, and adjust the distance between the indenter 10 and the tooling. Place the metal specimen 1 frozen in liquid nitrogen on the support plate 4. At the same time, the detection groove 3 on the surface of the metal specimen 1 is parallel to the support plate 4, the surface where the detection groove 3 is located faces downward, the support plate 4 and the detection groove 3 are parallel to the indenter 10 of the press 9. Then, operate the press 9 to quickly apply pressure to the defective part of the metal specimen 1 through the indenter 10. The displacement speed of the indenter 10 dropping >2 mm / s. Among them, the time from taking out the specimen from the liquid nitrogen environment to fracturing should be minimized and not exceed 2 min, so as to ensure that the specimen is in a low-temperature state during fracturing. The notch tip of the detection groove 3 of the specimen cracks due to stress concentration, and the crack rapidly propagates under the action of pressure. The metal specimen 1 brittlely fractures into two sections along the V-shaped notch of the detection groove 3, and the fracture surface is a bright and smooth brittle fracture surface, and the defective part can be completely exposed in the middle of the fracture surface.

[0060] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting internal defects in a metal specimen, characterized in that, it comprises the following steps: Cut a metal piece with internal defects (2) to obtain a metal specimen (1); Open a detection groove (3) parallel to the internal defects (2) on the surface of the metal specimen (1); Perform liquid nitrogen treatment on the metal specimen (1) with the detection groove (3) opened; After the liquid nitrogen treatment, apply pressure to the surface of the metal specimen (1) to break the metal specimen (1) along the detection groove (3) and expose the internal defects (2); Analyze the internal defects (2) exposed on the metal specimen (1).

2. The method for detecting internal defects in a metal specimen according to claim 1, characterized in that, Cutting a metal piece with internal defects (2) to obtain a metal specimen (1) includes the following steps: Detect the position of the internal defects (2) in the metal piece; Cut the metal piece with the position of the internal defects (2) as the center to obtain a metal specimen (1) with a rectangular block structure, and the internal defects (2) are located at the center of the metal specimen (1).

3. The method for detecting internal defects in a metal specimen according to claim 1, characterized in that, Opening a detection groove (3) parallel to the internal defects (2) on the surface of the metal specimen (1) includes: Open a V-shaped detection groove (3) on the surface of the metal specimen (1) with a rectangular block structure. The detection groove (3) extends from one end of the metal specimen (1) to the other end, with a depth of 3 mm to 5 mm and is located in the middle of the surface of the metal specimen (1).

4. The method for detecting internal defects in a metal specimen according to claim 1, characterized in that, Performing liquid nitrogen treatment on the metal specimen (1) with the detection groove (3) opened includes: Put the metal specimen (1) into liquid nitrogen at -196°C to -210°C for freezing and keep it warm for ten minutes.

5. The method for detecting internal defects in a metal specimen according to claim 1, characterized in that, Applying pressure to the surface of the metal specimen (1) to break the metal specimen (1) along the detection groove (3) and expose the internal defects (2) includes the following steps: Place the metal specimen (1) taken out of the liquid nitrogen on the tooling with the detection groove (3) facing down; Apply pressure to the metal specimen (1) through the indenter (10) of the press (9) until the metal specimen (1) breaks along the detection groove (3) and exposes the internal defects (2).

6. The method for detecting internal defects in a metal specimen according to claim 5, characterized in that, When the indenter (10) of the press (9) applies pressure, the descending speed > 2 mm / s.

7. The method for detecting internal defects in a metal specimen according to claim 5, characterized in that, The time period from taking the metal specimen (1) out of the liquid nitrogen to the metal specimen (1) breaking along the detection groove (3) is less than 2 minutes.

8. A detection device for internal defects in a metal specimen, characterized in that, For the method for detecting internal defects in a metal specimen according to any one of claims 1-7, it includes a tooling and a press (9); The tooling includes a support plate (4) and a bottom plate (5). There are two bottom plates (5) which are parallel to each other and are installed on the surface of the bottom plate (5) through fastening screws (8) and are used to support the metal specimen (1); The bottom plate (5) is placed under the press (9); The press (9) is equipped with a punch (10), and the punch (10) is used to apply pressure to the surface of the metal specimen (1).

9. A detection device for internal defects of a metal specimen according to claim 8, characterized in that, a chute (6) is formed in the bottom surface of the bottom plate (5), a locking groove (7) is formed in the bottom surface of the chute (6), the stud of the fastening screw (8) passes through the locking groove (7) and is threadedly connected to the support plate (4), and the inner diameter of the inscribed circle of the nut of the fastening screw (8) is greater than the width of the locking groove (7); The chute (6) is parallel to the locking groove (7) and perpendicular to the support plate (4).

10. A detection device for internal defects of a metal specimen according to claim 8, characterized in that, when the support plate (4) supports the metal specimen (1), the detection groove (3) of the metal specimen (1) is parallel to the support plate (4) and is located between the two support plates (4).

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