Method for testing internal stress of copper alloy strip based on etching

Abstract

The invention provides an etching-based copper alloy strip internal stress inspection method, and relates to the technical field of copper alloy strip inspection. The method for testing the internal stress of the copper alloy strip comprises the following steps: firstly, establishing an internal stress value-etching warping degree contrast curve of a copper alloy with a specific mark and specification through a standard method; selectively pasting a film on the strip sample to be measured, and accurately measuring the initial warping height of the strip sample; carrying out controllable spraying etching on the reserved window of the sample by using a ferric trichloride etching solution with a specific ratio until penetration; measuring the warping height after etching and calculating the warping degree; and finally, converting the measured warping degree into an actual internal stress value based on the contrast curve. According to the method, rapid macroscopic deformation of chemical etching and accurate calibration of a standard method are combined, interference of mechanical trepanning on measurement accuracy is eliminated, quantitative detection of the internal stress of the copper alloy strip is achieved, and the method has the advantages of being easy and convenient to operate, low in cost, accurate and reliable in detection result, high in efficiency and the like.

Description

Technical Field

[0001] This invention relates to the field of copper alloy strip testing technology, specifically to a simple, accurate, and efficient method for detecting internal stress etching in copper alloy strips. It is applicable to the production quality control and rapid quantitative detection of internal stress in copper alloy strips (such as brass, bronze, cupronickel, etc.) used in the fields of electronics, electrical engineering, automobiles, and aerospace. Background Technology

[0002] Copper and copper alloy strips are widely used in electronics, electrical engineering, automotive manufacturing, and aerospace due to their excellent electrical and thermal conductivity, ductility, and corrosion resistance. During production, rolling, cutting, and bending processes inevitably introduce internal stress into the material. Excessive internal stress can cause warping, twisting, or even cracking of the strip during subsequent processing or use, severely affecting the dimensional accuracy, assembly performance, and service life of the product. Therefore, accurately and quickly detecting the internal stress level of copper alloy strips is crucial for optimizing production processes and controlling product quality.

[0003] Currently, common methods for detecting internal stress mainly include: 1. X-ray diffraction method: High precision, but expensive equipment, complex operation, demanding requirements on the test environment and sample surface, and difficult to achieve rapid on-site detection.

[0004] 2. Stress relaxation method: Stress is calculated by measuring the strain change after stress release, but the test cycle is extremely long (up to tens of hours), which is inefficient and not suitable for quality control in a fast-paced production environment.

[0005] 3. Drilling method: This method requires attaching strain gauges around the drilled hole, which is cumbersome. The results are also greatly affected by the drilling and attachment process, resulting in poor repeatability. Furthermore, the drilling process introduces new processing stresses, interfering with the accuracy of the measurements.

[0006] 4. Strip Cutting Method: This method involves cutting the strip into narrow strips to release the constraint along its length. The magnitude of internal stress is characterized by measuring the warpage or length variation. Its disadvantages are that the direction of constraint release in the narrow strips is one-dimensional, and the magnitude of internal stress cannot be quantitatively obtained. Furthermore, the strip cutting process introduces new processing stresses, interfering with the accuracy of the measurement.

[0007] The aforementioned methods, due to their high cost, low efficiency, or complex operation, are insufficient to meet the demand for rapid, low-cost, and convenient testing of large batches of samples on copper alloy strip production lines. Therefore, developing a simple, low-cost, efficient, and reliable method for detecting internal stress in copper alloy strips is of significant practical importance. Summary of the Invention

[0008] To address the problems in the background art, this invention provides a method for inspecting the internal stress of copper alloy strips based on etching, the purpose of which is: 1. Simplify the testing process and reduce the professional skills required of operators; 2. Reduces investment costs in testing equipment, eliminating the need for expensive and precision instruments; 3. Shorten the testing cycle and enable rapid testing of batch samples; 4. Improve the accuracy and repeatability of test results, providing reliable data support for production process optimization.

[0009] To achieve the above objectives, the core technical solution adopted by this invention is as follows: a quantitative comparison curve of "internal stress value - etching warpage" is established in advance, the sample is made to undergo natural deformation without external force interference by penetrating etching, the warpage of the sample is measured, and finally the internal stress value of the copper alloy strip is calculated based on the comparison curve.

[0010] Specifically, the present invention adopts the following technical solution: An etching-based method for testing the internal stress of copper alloy strip includes the following steps: S1: Establish a comparison curve between the internal stress σ of the copper alloy strip and the warpage WD of the sample; S2: Prepare the sample according to size a×b; S3: Apply a film to the sample, reserve a window of size c×c at the designated position of the film, and then measure the initial warpage height h of the sample; S4: Perform through-etching on the window portion of the sample, then measure the final warpage height H of the sample according to the formula. Calculate the warpage WD of the sample; S5: The internal stress value of the copper alloy strip is obtained quantitatively based on the reference curve.

[0011] Further improve the technical solution: In S1, for copper alloy strips of a specific grade and specification, prepare a series of standard samples with different internal stress levels, and use the standard stress measurement method to determine their actual internal stress value σ. Then, according to steps S2-S4, obtain their corresponding warpage WD. Plot a scatter plot with the actual internal stress value σ as the abscissa and the warpage WD as the ordinate, and perform linear regression fitting to obtain the reference curve for the copper alloy of that grade and specification.

[0012] Further improve the technical solution: The standard stress measurement method is X-ray diffraction.

[0013] Further improve the technical solution: In S2, a rectangular sample is cut along the rolling direction of the copper alloy strip, and the sample size is trimmed to ensure that the long side a=300mm and the wide side b=60mm; In S3, the center of the window is located at 250mm on the long side and 30mm on the wide side of the sample, and the side length of the window is c=5-10mm.

[0014] Further improve the technical solution: In S3, wipe the sample surface with anhydrous ethanol before applying the film and then dry it; after applying the film, press the film with a pressure roller or block with a pressure of 0.01-0.05MPa to ensure that the film adheres tightly to the sample surface.

[0015] Further improvement of the technical solution: In S4, an etching solution is used to perform penetration etching on the window area of ​​the sample. The etching solution is a mixed solution of ferric chloride, deionized water and anhydrous ethanol, with a mass ratio of ferric chloride:deionized water:anhydrous ethanol = 4:5:1.

[0016] Further improvements to the technical solution: etching solution temperature is 30℃-50℃, spray pressure is 0.2-0.4 bar, and sample conveying speed is 10-80 mm / s.

[0017] Further improve the technical solution: When measuring the initial warpage height h or the final warpage height H of the sample, place the sample on the platform and make one wide side of the sample fit against the platform. Then measure the warpage height of the other wide side of the sample. Measure at least 5 points and take the maximum value.

[0018] After implementing the above technical solution, compared with the prior art, the present invention can produce the following beneficial effects: 1. Compared to drilling and slitting methods, penetration etching is a chemical process without mechanical external force, and will not introduce processing stress that interferes with the accuracy of measurement.

[0019] 2. This invention can quantitatively obtain the internal stress value of copper alloy strip by comparing the curve, providing clear guidance for production process optimization (such as adjusting rolling parameters, annealing temperature, etc.) and reducing the product defect rate caused by internal stress.

[0020] 3. Simple operation, lowering the testing threshold: No expensive precision instruments are required, only conventional etching test machines and basic measuring tools are needed. The testing process is standardized, and operators can get started after simple training. It is suitable for rapid on-site testing on the production line.

[0021] 4. High testing efficiency and suitable for batch production: The testing cycle for a single sample is only 30-60 minutes, and multiple samples can be tested simultaneously. This solves the problems of long testing cycles and inability to conduct batch testing in traditional methods, and meets the high-efficiency quality control needs of industrial production.

[0022] 5. Accurate and reliable test results: Effectively reduces systematic and random errors, with a relative standard deviation (RSD) of ≤3% and good repeatability.

[0023] 6. Low cost and high practicality: The reagents used (ferric chloride, anhydrous ethanol, and deionized water) are all conventional chemical raw materials, which are inexpensive and easy to obtain. The maintenance cost of the instruments and equipment is low, making them suitable for copper alloy strip production enterprises of all sizes. Attached Figure Description

[0024] Appendix Figure 1 The diagram shown is a schematic of the sample film application.

[0025] Appendix Figure 2 The diagram shown is a schematic diagram of the measurement of the warp height of the sample.

[0026] In the attached diagram: 1. Sample; 2. Film; 3. Window; 4. Platform; 5. Height gauge. Detailed Implementation

[0027] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these preferred embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0028] An etching-based method for testing the internal stress of copper alloy strip includes the following steps: Calibration phase: Establishing a control curve 1. Preparation of standard sample sets: Select a batch of C1100 copper strip (0.5mm thick) and deliberately prepare 6 master strips with internal stress levels distributed from low to high through different rolling deformation amounts or annealing processes. Cut rectangular samples along the rolling direction of the master strip and trim the sample dimensions to ensure that the long side a=300mm, the wide side b=60mm, and the tolerance is less than 0.1mm.

[0029] 2. Measurement of internal stress σ using standard method: The internal stress value of each standard specimen was measured and the data was recorded using an X-ray diffraction stress analyzer, strictly following the standard operating procedures.

[0030] 3. Etching method for measuring warpage (WD): For the above 6 standard samples, perform the following steps in sequence: 3.1 Wipe the standard sample with anhydrous ethanol and then dry it.

[0031] 3.2 Apply a film to the standard sample, leaving a window of size c×c at the designated location of the film application, and then measure the initial warpage height h of the standard sample.

[0032] See attached document Figure 1Cut an 8×8mm window 3 from the film 2, and then attach the film 2 to the sample 1, so that the center of the window 3 is located at 250mm on the long side and 30mm on the wide side of the sample. After attaching the film, press the film 2 with a pressure roller or block with a pressure of 0.01-0.05MPa to ensure that the film 2 is tightly attached to the surface of the sample 1, so as to prevent the etching solution from penetrating into the film and causing corrosion in non-target areas.

[0033] See attached document Figure 2 Place the sample 1 on the platform 4 and make one wide side of the sample 1 fit against the platform 4. Then use a height ruler 5 to measure the warping height of the other wide side of the sample. Measure at least 5 points and take the maximum value.

[0034] 3.3. Use an etching solution to perform penetration etching on the window area of ​​the standard sample, and then measure the final warpage height H of the standard sample according to the formula. Calculate the warpage WD of the standard sample. Specifically, the etching solution is a mixture of ferric chloride, deionized water, and anhydrous ethanol, with a mass ratio of ferric chloride:deionized water:anhydrous ethanol = 4:5:1. The etching solution temperature is 30℃-50℃, the spray pressure is 0.2-0.4 bar, and the standard sample is etched at a conveying speed of 15 mm / s until the window is penetrated.

[0035] 3.4 Repeat steps 3.1-3.3, plot a scatter plot with the actual internal stress value σ as the abscissa and the warpage WD as the ordinate, and perform linear regression fitting to establish a comparison curve of internal stress value and etching warpage for C1100 copper strip (thickness 0.5mm).

[0036] Application Stage: A roll of C1100 copper strip (0.5mm thick) needs to be tested for internal stress. The following steps should be performed sequentially: 1. Cut a sample (300mm×60mm) from the mother tape to be tested, clean and apply the film according to the same process as described above, and then measure the initial warp height h of the sample.

[0037] 2. Using the exact same etching process parameters (etching solution temperature 35℃, pressure 0.3 bar, conveyor speed 15mm / s), perform through-etching on the sample, measure the final warpage height H of the sample, and then calculate the warpage height H according to the formula. Calculate the warpage WD of the sample.

[0038] 3. The internal stress value of the copper alloy strip is obtained quantitatively based on the reference curve.

[0039] It is worth noting that the content not described in detail in the above embodiments is prior art. It is also worth noting that any additions, subtractions, substitutions, and improvements made by those skilled in the art based on the structure and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for inspecting internal stress in copper alloy strips based on etching, characterized in that: Includes the following steps: S1: Establish a comparison curve between the internal stress σ of the copper alloy strip and the warpage WD of the sample; S2: Prepare the sample according to size a×b; S3: Apply a film to the sample, reserve a window of size c×c at the designated position of the film, and then measure the initial warpage height h of the sample; S4: Perform through-etching on the window portion of the sample, then measure the final warpage height H of the sample according to the formula. Calculate the warpage WD of the sample; S5: The internal stress value of the copper alloy strip is obtained quantitatively based on the reference curve.

2. The method for testing the internal stress of copper alloy strip based on etching as described in claim 1, characterized in that: In step S1, a series of standard samples with different internal stress levels are prepared for copper alloy strips of a specific grade and specification. The actual internal stress value σ is determined by the standard stress measurement method. Then, according to steps S2-S4, the corresponding warpage WD is obtained. A scatter plot is drawn with the actual internal stress value σ as the abscissa and the warpage WD as the ordinate, and linear regression fitting is performed to obtain the reference curve for the copper alloy of that grade and specification.

3. The method for testing the internal stress of copper alloy strip based on etching as described in claim 2, characterized in that: The standard stress measurement method is X-ray diffraction.

4. The method for testing the internal stress of copper alloy strip based on etching as described in claim 1, characterized in that: In S2, a rectangular sample is cut along the rolling direction of the copper alloy strip, and the sample size is trimmed to ensure that the long side a=300mm and the wide side b=60mm; in S3, the center of the window is located at 250mm on the long side and 30mm on the wide side of the sample, and the side length of the window is c=5-10mm.

5. The method for testing the internal stress of copper alloy strip based on etching as described in claim 1, characterized in that: In S3, the sample surface is wiped with anhydrous ethanol before applying the film and then dried. After applying the film, the film is pressed with a pressure roller or block with a pressure of 0.01-0.05MPa to ensure that the film adheres tightly to the sample surface.

6. The method for testing the internal stress of copper alloy strip based on etching as described in claim 1, characterized in that: In S4, an etching solution is used to perform penetration etching on the window area of ​​the sample. The etching solution is a mixed solution of ferric chloride, deionized water and anhydrous ethanol, with a mass ratio of ferric chloride:deionized water:anhydrous ethanol = 4:5:

1.

7. The method for testing the internal stress of copper alloy strip based on etching as described in claim 6, characterized in that: The etching solution temperature is 30℃-50℃, the spray pressure is 0.2-0.4 bar, and the sample conveying speed is 10-80 mm / s.

8. The method for testing the internal stress of copper alloy strip based on etching as described in claim 1, characterized in that: When measuring the initial warp height h or the final warp height H of the specimen, place the specimen on the platform and make one wide side of the specimen fit against the platform. Then measure the warp height of the other wide side of the specimen. Measure at least 5 points and take the maximum value.

Images