A method for measuring the bond strength of a cast repair process

Abstract

This invention discloses a method for measuring the bonding strength of a casting repair process, solving the problem in the prior art where the bonding strength of the casting repair process cannot be quantitatively obtained. It has the beneficial effect of accurately obtaining the bonding strength between the casting substrate and the repair layer, achieving quantitative strength measurement. The specific solution is as follows: A method for measuring the bonding strength of a casting repair process includes: preparing a specimen; cutting a groove in the specimen; cutting the specimen at the groove to obtain the substrate; repairing the cut specimen, with the repair layer covering the groove; breaking the repaired specimen and recording the maximum tensile force; and calculating the bonding strength between the substrate and the repair layer based on the maximum tensile force.

Description

Technical Field

[0001] This invention relates to the field of casting repair, and in particular to a method for measuring the bonding strength of casting repair processes. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] During the production and processing of castings, surface defects such as porosity, sand holes, and material shortages are unavoidable. To reduce manufacturing costs and without affecting the performance of the castings, repair processes are used to salvage and reuse them. Commonly used repair processes include hot welding, cold welding, and brush plating. Currently, the industry primarily uses qualitative measurement methods to test the bonding strength between the casting substrate and the repair layer, including filing, scratch testing, and thermal shock testing.

[0004] Filing test: Use a double-toothed file at approximately a 45° angle to the surface of the repair layer, and file the edge of the repair layer from the base metal toward the repair layer. Observe the repair layer near the file. The repair layer should not peel off or lift.

[0005] Scratch test: Use a Φ5mm scratcher with a 15° sharp point to scratch the surface of the repaired part. There should be no peeling or flaking around the scratch.

[0006] Thermal shock test: Heat to 200±10℃, keep warm for 1 hour and then cool with water. Repeat this process 50 times. No bubbling or shelling should occur.

[0007] Qualitative measurement methods are based on the differences in the physical and mechanical properties of the repair layer metal and the base metal to check for poor bonding in the repair layer. The inventors discovered that whether it is the filing method, scratch method, or thermal shock method, they can only qualitatively detect whether the bonding between the base and the repair layer is good after the casting is repaired. They cannot accurately measure the bonding strength between the base and the repair layer, and therefore cannot gain customer approval for the reliability of the casting repair process. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for measuring the bonding strength of the casting repair process, which can accurately obtain the bonding strength between the casting substrate and the repair layer, and realize the quantitative measurement of strength.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0010] A method for measuring the bonding strength of a casting repair process, comprising the following:

[0011] Prepare test specimens;

[0012] Grooving is performed on the specimen;

[0013] The specimen is cut off at the groove to obtain the matrix;

[0014] Repair the cut specimen, and cover the cut groove of the specimen with the repair layer;

[0015] Pull the repaired specimen to break and record the maximum tensile force at break.

[0016] The bonding strength between the substrate and the repair layer is calculated based on the maximum tensile force at break.

[0017] As described above, in a method for measuring the bonding strength of a casting repair process, the bonding strength σ between the substrate and the repair layer is equal to the maximum tensile force at breakage, Fb, and the cross-sectional area So, where the cross-sectional area refers to the cross-sectional area of ​​the repair layer at the cut point of the specimen.

[0018] The cross-sectional area of ​​the repair layer at the cut point of the specimen is calculated by subtracting the cross-sectional area after the groove is cut from the cross-sectional area after the specimen is repaired. The cross-sectional area after the specimen is repaired is the same as the original cross-sectional area at the cut point of the specimen.

[0019] In the above-described method for measuring the bonding strength of a casting repair process, the grooving treatment of the specimen is performed in the middle part of the specimen.

[0020] The method for measuring the bonding strength of a casting repair process as described above, wherein the grooving treatment of the specimen refers to cutting an annular groove into the specimen.

[0021] The method for measuring the bonding strength of a casting repair process as described above, wherein the inner diameter of the annular groove is 15-18 mm and the length of the annular groove is 8-12 mm;

[0022] The diameter of the specimen is 19-22 mm and the length of the specimen is 18-23 cm.

[0023] The method for measuring the bonding strength of a casting repair process, as described above, involves grooving the specimen using a lathe. The specimen is held in place on the lathe before grooving, which is very convenient.

[0024] The method for measuring the bonding strength of a casting repair process as described above involves testing the repaired specimen by tensile testing with a strength tester.

[0025] The above-described method for measuring the bonding strength of a casting repair process involves setting up 4-7 test pieces, and calculating the bonding strength of each test piece after grooving, cutting, repairing, tensile testing, and so on.

[0026] The above-described method for measuring the bonding strength of a casting repair process involves gray cast iron, ductile iron, vermicular graphite cast iron, or cast aluminum. By measuring different types of specimens, the bonding strength values ​​of the repair process for different types of castings are obtained, thereby acquiring different casting repair strengths.

[0027] The above-described method for measuring the bonding strength of a casting repair process involves repairing a cut specimen using methods including hot welding, cold welding, or brush plating.

[0028] The beneficial effects of the present invention are as follows:

[0029] 1) This invention provides a measurement method that involves grooving, cutting, and repairing the specimen, followed by tensile testing to obtain the maximum tensile force value. This method can accurately determine the bonding strength between the casting substrate and the repair layer, providing an objective numerical representation of the bonding strength of the casting repair process. This is more intuitive and convincing.

[0030] 2) The present invention cuts an annular groove into the specimen, which is convenient for processing, cutting and repairing the specimen, and subsequent tensile testing, making the overall process more convenient.

[0031] 3) This invention sets up multiple test pieces, and calculates the grooving, cutting, repairing, tensile breaking and bonding strength of each test piece. The accuracy of the measurement method is ensured by using multiple values. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 This is a flowchart illustrating the bonding strength of a casting repair process according to one or more embodiments of the present invention. Detailed Implementation

[0034] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] As described in the background section, there is a problem in the prior art that the bonding strength of casting repair processes cannot be quantitatively obtained. In order to solve the above technical problem, this invention proposes a method for measuring the bonding strength of casting repair processes.

[0037] Example 1

[0038] In a typical embodiment of the present invention, reference is made to Figure 1 As shown, a method for measuring the bonding strength of a casting repair process includes the following:

[0039] Prepare test specimens;

[0040] Grooving is performed on the specimen;

[0041] The specimen is cut off at the groove to obtain the matrix;

[0042] Repair the cut specimen, and cover the cut groove of the specimen with the repair layer;

[0043] Pull the repaired specimen to break and record the maximum tensile force at break.

[0044] The bonding strength between the substrate and the repair layer is calculated based on the maximum tensile force at break.

[0045] The bonding strength between the substrate and the repair layer σ = the maximum tensile force at break Fb / cross-sectional area So.

[0046] Regarding the cross-sectional area, it refers to the cross-sectional area of ​​the repair layer at the cut point of the specimen. The cross-sectional area of ​​the repair layer at the cut point of the specimen is calculated by subtracting the cross-sectional area after the groove is cut from the cross-sectional area after the specimen is repaired.

[0047] Grooving the specimen involves cutting a groove in the middle of the specimen. Specifically, grooving the specimen means cutting an annular groove into the specimen.

[0048] In this embodiment, the specimen is a test rod with a set length and a set diameter. The middle section of the test rod is a reduced-diameter section, meaning that the diameters at both ends of the test rod are larger than the diameter of the middle section. Specifically, an annular groove is cut in the middle of the middle section of the test rod with a smaller diameter. The annular groove is along the circumferential direction of the specimen. In some examples, the diameter of the specimen is 19-22 mm, specifically 20 mm; the length of the specimen is 18-23 cm, specifically 20 cm; the diameter of the middle section of the specimen is 18 mm; the inner diameter of the annular groove is 15-18 mm, specifically 17 mm; and the length of the annular groove (along the central axis of the specimen) is 8-12 mm, specifically 10 mm.

[0049] Thus, in this embodiment, the cross-sectional area So = π*10*10 - π*8.5*8.5, where 8.5 is the radius of the cut end of the test rod.

[0050] Grooving the specimen involves using a lathe to cut the grooves. In some examples, the specimen is clamped on a lathe and then grooved in the circumferential direction, which is very convenient. After grooving, the specimen is cut circumferentially in the middle of the annular groove using a lathe to achieve severance.

[0051] Specifically, the repaired specimen is broken by a tensile testing machine. The maximum tensile force Fb can be obtained at the moment of breakage. It can be understood that the tensile testing machine is existing technology.

[0052] In some examples, a total of 4-7 specimens were set up, and the grooving, cutting, repair, tensile strength and bonding strength of all specimens were calculated.

[0053] The castings are made of gray cast iron, ductile iron, vermicular graphite cast iron, or cast aluminum. By measuring the bonding strength of different types of castings, the bonding strength of different types of castings is obtained, so as to obtain the different casting repair strengths.

[0054] In addition, the cut specimens are repaired using methods including hot welding, cold welding, or brush plating.

[0055] In this embodiment, the measurement method includes the following:

[0056] 1) First, cast 6 HT250 (gray cast iron) single-cast test bars, and after cooling, process them into single-cast φ20mm uncut test bars that conform to GB / T9439 (national standard gray cast iron parts);

[0057] 2) Cut a φ17mm and 10mm long annular groove in the middle of the single-cast test bar using a lathe;

[0058] 3) Cut the test bar along the diameter plane of the test bar using a lathe at the middle part of the annular groove;

[0059] 4) Using the casting cold welding repair process, the two sections of the test bar were repaired along the annular groove into a test bar with a diameter of φ20mm;

[0060] 5) Break the repaired test bar on a tensile strength tester and record the maximum tensile force value Fb.

[0061] 6) Calculate the bonding strength σ = bonding force Fb / cross-sectional area So.

[0062] Table 1. Test results of 6 HT250 single-cast test bars

[0063] Test No. Submission Number Sample Name Material Specifications Diameter of a single-cast test bar (mm) Diameter of mating surface (mm) Maximum bonding force (kN) Bond strength (MPa) other 19-1 1 Test bar 1 HT250 20 17 16.87 193.61 19-2 2 Test Rod 2 HT250 20 17 25.04 287.37 19-3 3 Test bar 3 HT250 20 17 19.92 228.61 19-4 4 Test bar 4 HT250 20 17 21.95 251.91 19-5 5 Test bar 5 HT250 20 17 25.18 288.98 19-6 6 Test bar 6 H1250 20 17 19.68 225.86

[0064] Table 1 shows the test results for the six test bars. Except for the first one, which is less than 200 MPa, the bond strength of the others is greater than 220 MPa. The presented values ​​can intuitively show the bond strength between the substrate and the repair layer, indicating that the repaired casting also has good bond strength and can meet the usage requirements. This shows that the measurement method can accurately obtain the bond strength value of the cold welding repair process of castings, which is convenient for persuading customers to accept the casting repair process, repairing casting defects that meet technical standards, and reducing losses.

[0065] Therefore, the method provided in this embodiment is a quantitative measurement method, which fills the gap in the industry for measuring the bonding strength of casting repair processes. It can accurately measure the value of the bonding strength of casting repair processes, ensuring the reliability of casting repair processes. It presents the bonding strength of casting repair processes with objective values, which is more intuitive and convincing.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of measuring the bond strength of a casting repair process characterized by, Includes the following: Prepare test specimens; The specimen is grooved; the grooving process refers to cutting an annular groove into the specimen; the annular groove is along the circumferential direction of the specimen; The specimen is cut off at the groove to obtain the matrix; Repair the cut specimen, with the repair layer covering the cut groove of the specimen; fill the cut groove of the specimen with the repair layer, and after filling and repair, the outer diameter of the specimen in the repair area is the same as the outer diameter of the specimen in that area before cutting the groove; Pull the repaired specimen to break and record the maximum tensile force at break. The bonding strength between the substrate and the repair layer is calculated based on the maximum tensile force at break. The bonding strength between the substrate and the repair layer is σ = the maximum tensile force at break Fb / cross-sectional area So. The cross-sectional area refers to the cross-sectional area of ​​the repair layer at the cut point of the specimen. The cross-sectional area of ​​the repair layer at the cut point of the specimen is obtained by subtracting the cross-sectional area of ​​the specimen after the groove is cut from the cross-sectional area of ​​the specimen after repair at the cut point.

2. A method of measuring the strength of the bond of a casting repair process according to claim 1, characterized in that, The groove cutting process is performed on the middle part of the specimen.

3. The method for measuring the bonding strength of a casting repair process according to claim 1, characterized in that, The inner diameter of the annular groove is 15-18mm, and the length of the annular groove is 8-12mm; The diameter of the specimen is 19-22 mm and the length of the specimen is 18-23 cm.

4. The method for measuring the bonding strength of a casting repair process according to claim 1, characterized in that, The grooving process of the specimen is performed by grooving the specimen on a lathe.

5. The method for measuring the bonding strength of a casting repair process according to claim 1, characterized in that, The repaired specimen will be broken using a tensile testing machine.

6. The method for measuring the bonding strength of a casting repair process according to claim 1, characterized in that, A total of 4-7 specimens were set up, and the grooving, cutting, repair, tensile strength and bonding strength of each specimen were calculated.

7. The method for measuring the bonding strength of a casting repair process according to claim 1, characterized in that, The casting is made of gray cast iron, ductile iron, vermicular graphite cast iron, or cast aluminum.

8. The method for measuring the bonding strength of a casting repair process according to claim 1, characterized in that, The repair of the cut specimen includes hot welding, cold welding, or brush plating repair processes.

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