A method for testing the brittle fracture properties of coated iron plates

Abstract

This invention discloses a method for detecting the brittle fracture of coated iron plates, including sample preparation, sample cupping processing, and sample cupping data analysis steps. This method simulates the adhesion of the film when the iron cracks at the cut during can / lid manufacturing. The adhesion area of ​​the film determines whether the coated iron will develop stringing defects in subsequent can / lid manufacturing processes, eliminating the need for actual can / lid manufacturing. Furthermore, this invention uses a hemispherical mold to directly press the coated iron plate until the iron cracks. The ratio of the length of the film extending beyond the iron edge at the crack location to the total crack length is measured to determine whether the coated iron will develop elongation defects at the cut during subsequent can / lid manufacturing processes, again eliminating the need for actual can / lid manufacturing. This provides a simple, rapid, and reliable method for detecting the brittle fracture of coated iron plate samples.

Description

Technical Field

[0001] This invention relates to the field of performance testing technology for metal packaging materials, specifically a method for testing the brittle fracture properties of coated iron sheets. Background Technology

[0002] Coated steel used in the metal packaging field is a packaging material that combines the advantages of both metal and plastic by laminating steel plates with a thickness range of 0.13mm-0.6mm and films with a thickness range of 12um-25um. Because plastic films have a higher elongation at break than coatings, coated steel has excellent deep-drawing performance and is often used as a substitute for coated steel in the fields of food, beverage, and chemical metal packaging.

[0003] While coated steel products offer numerous performance advantages over painted steel, they can also present challenges when used in can / lid manufacturing. For instance, during processes like stamping and trimming where the coated steel needs to be cut, if the die blade is not sharp or the die is designed to break rather than cut, the film can easily be stretched and stringy at the break point. This incomplete film breakage can leave film residue at the cut of the finished can / lid, affecting can / lid manufacturing efficiency, damaging the die, and even causing contamination of the contents.

[0004] Currently, the industry has successively formulated national standards for the testing and evaluation methods and product standards of metal packaging materials containing coatings or films, such as GB / T 40871-2021 "Thermo-coated Steel Sheets and Strips with Plastic Film", GB / T 41899-2022 "General Quality Rules for Tin- or Chrome-plated Thin Steel Sheets for Food Containers", and GB / T43951-2024 "General Quality Rules for Coated Iron and Coated Aluminum for Food Containers". However, these standards do not include methods for testing whether coated iron has this insufficient brittleness. It can only be determined through actual use by can / lid manufacturers, which is a post-production test. By this time, coated iron is often already in mass production, which greatly hinders its promotion and application in downstream industries. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting the brittle fracture of coated iron plates, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for detecting the brittle fracture property of coated iron plates, comprising:

[0007] S1: Use clamps to secure the coated iron plate sample;

[0008] S2: When the driving device is used, the die head presses into the coated iron plate sample, causing the coated iron plate sample to deform until the coated iron cracks;

[0009] S3: Measure the ratio of the total crack length extending from the iron edge to the location of the iron crack;

[0010] S4: If the ratio of the length of the membrane extending from the iron edge at the location of the iron crack to the total crack length is greater than or equal to 0.8, the brittle fracture test of the coated iron plate is: unqualified;

[0011] Preferably, the length of the iron crack is 5 mm or more.

[0012] Preferably, the die head is hemispherical with a diameter of 18-22 mm, and the die head presses into the coated iron at a speed greater than 0.1 mm / s.

[0013] Preferably, the area of ​​the coated iron plate sample is larger than that of the mold head.

[0014] Preferably, the coated iron plate sample is prepared by hot-melt method or adhesive method, and the thickness of the coated iron film is 12μm-25μm.

[0015] Preferably, the driving device is a cupping machine.

[0016] Preferably, the cupping machine is equipped with an automatic feeding and positioning structure on its external side. The automatic feeding and positioning structure includes a mounting box, which is fixed to the side of the cupping machine. A driver is installed inside the mounting box. A rotating connecting plate is connected to the output shaft of the driver. A sample plate is connected to the other end of the rotating connecting plate. A sample port is opened inside the sample plate. A pressure pad is provided inside the sample port. A sliding groove is opened inside the cupping machine.

[0017] Preferably, there are two sets of slides, and the two sets of slides are arranged opposite to each other.

[0018] Preferably, the connecting plate has an inclined limiting groove in the middle.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] By directly pressing a coated iron plate into a hemispherical mold until the iron cracks, the ratio of the length of the film extending from the iron edge at the crack location to the total crack length is measured to determine whether the coated iron will produce a stringing defect at the cut during subsequent can / lid making. This provides a simple, fast, and reliable detection method for the brittle fracture of coated iron plate samples without the need for actual can / lid making. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the cupping mechanism of the present invention;

[0022] Figure 2 This is a top view of the cupping machine of the present invention;

[0023] Figure 3 This is a top cross-sectional view of the automatic feeding and positioning structure of the present invention.

[0024] Figure 4 This is a schematic diagram of the sample plate cross-sectional structure from the side and top views.

[0025] Figure 5 This is a schematic diagram of the sample port structure of the present invention;

[0026] Figure 6 This is a schematic diagram of the unstretched coated iron plate sample of the present invention;

[0027] Figure 7 This is a schematic diagram of the wire drawing process for the coated iron plate sample of the present invention.

[0028] In the diagram: cupping machine-a, control panel-b, automatic feeding and positioning structure-1, mounting box-11, driver-12, rotating connecting plate-13, sample plate-14, sample port-15, pressure pad-16, slide groove-17. Detailed Implementation

[0029] To further explain the technical solution of the present invention, a detailed description is provided below through specific embodiments.

[0030] This invention provides a method for testing the brittle fracture properties of coated iron plates, comprising: fixing a coated iron plate sample with a clamp; pressing a hemispherical die into the coated iron plate until the iron cracks; the diameter of the hemispherical die is 18-22 mm; the hemispherical die is driven by a device at a speed greater than 0.1 mm / s to deform the coated iron until the coated iron cracks by more than 5 mm; measuring the ratio of the length of the membrane extending beyond the iron edge at the crack location to the total crack length; alternatively, the ratio of the area extending beyond the iron edge to the total crack area can also be used, and this is not limited here; if the ratio of the length of the membrane extending beyond the iron edge at the crack location to the total crack length is greater than or equal to 0.8, the brittle fracture test of the coated iron plate is: unqualified;

[0031] The driving device is a cupping machine a, and an automatic feeding and positioning structure 1 is installed on the external side of the cupping machine a;

[0032] By directly pressing a coated iron plate into a hemispherical mold until the iron cracks, the ratio of the length of the film extending from the iron edge at the crack location to the total crack length is measured to determine whether the coated iron will develop a stretching defect at the cut during subsequent can / lid making. This method provides a simple, fast, and reliable test for the brittle fracture of coated iron plate samples without the need for actual can / lid making.

[0033] A 0.28mm thick coated iron plate sample was taken with a 15µm polyethylene terephthalate (PET) film on side A and a 19µm PET film on side B. To evaluate the brittle fracture of the coated iron, a coated iron plate sample with a length of 50mm and a width of 140mm was taken, placed in a fixture and clamped. A hemispherical punch with a diameter of 20mm was used to press from side A into side B at a pressing speed of 0.2mm / s. The coated iron cracked at the top of the hemispherical punch until the crack length was more than 5mm, and then the pressure was stopped. The ratio between the length of the film that was stretched and the total length of the crack was measured.

[0034] Example 1:

[0035] Methods to determine whether coated steel sheets will develop wire drawing defects during subsequent tube / cap manufacturing processes:

[0036] Take samples of coated iron plates and cut them into circular samples with a diameter of 50 mm. Place the test surface in a cupping machine (a). Set the cupping machine (a) to a speed of 0.2 mm / s-0.8 mm / s and press it into multiple points on the sample. The cupping crack length is 8-12 mm. Measure r and L, and calculate W.

[0037] r = the length of iron occupied by the membrane elongation

[0038] L = Total length of the crack in the iron

[0039] W=r / L

[0040] W≥0.8, is considered unqualified.

[0041] Compared with the prior art, the beneficial effect of Embodiment 2 is that: by simulating the adhesion of the film when the iron cracks at the cut during the production of coated iron cans / lids using a cupped plate, the adhesion area of ​​the film can be used to determine whether the coated iron will produce wire-drawing defects in the subsequent can / lid production process, i.e. whether the brittle fracture is qualified. This method does not require actual can / lid production for judgment and provides a reliable testing method for the factory inspection of coated iron products.

[0042] Example 2:

[0043] A 0.14mm thick coated iron plate sample was prepared. Side A was coated with a 19µm polyethylene terephthalate (PET) film, and side B with a 12µm PET film. The sample dimensions were 50mm in length and 70mm in width. It was clamped in a fixture, and a hemispherical die with a diameter of 18mm was used to press it from side B into side A at a speed of 0.8mm / s until the iron deformation crack length reached 5mm. r and L were measured, and W was calculated.

[0044] r = the length of iron occupied by the membrane elongation

[0045] L = Total length of the crack in the iron

[0046] Calculate W=r / L

[0047] W≥0.8, is considered unqualified.

[0048] The problem addressed in Example 3 is how to simulate the following behavior of the film and iron cracking after die stamping during can / lid making, using a coated iron plate sample. Because the film on coated iron is typically over 12µm thick to ensure barrier properties, and it adheres tightly to the iron surface, during die stamping, the upper and lower dies move relative to each other on the two surfaces of the coated iron, causing the iron to fracture under shear force. The film fractures along with the iron, and in this case, the film does not elongate at the fracture surface of the iron. However, if a cutting edge of the die becomes dull over long-term use, or if the die is severely worn due to prolonged use, or if the clearance between the upper and lower dies is too large, the shear gap between the die and the material will be too wide. Under the action of shear force, the film may elongate along the iron crack, resulting in the final product exhibiting a film edge extending beyond the iron edge, creating a film stringing phenomenon. This is unacceptable in the food packaging industry because it involves foreign matter contamination and causes significant problems for subsequent processing.

[0049] In Example 2, a hemispherical die is used to press the coated iron until the iron deforms and cracks. At this point, the film is not cut by shear force but torn. Observing the synchronization of the film and iron fracture in this situation can reflect the fracture of the film under conditions such as a dull die during actual stamping. This method is simple and easy to operate, and can effectively reflect the possibility of the coated iron fraying during the stamping process even when the coated iron is flat.

[0050] In this method, the speed of the cupping is not strictly limited because the purpose is to break the iron. However, maintaining a constant speed will make the results more accurate. This method is applicable to the evaluation of various samples of coated iron used in metal packaging.

[0051] .

[0052] The above testing methods are not limited to coated iron materials with SR or DR materials as the base material.

[0053] Please see Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5This invention provides a method for detecting the brittle fracture of coated iron plates, which includes an automatic feeding and positioning structure 1. The automatic feeding and positioning structure 1 includes a mounting box 11, which is fixed to the side of a cupping machine a. A driver 12 is installed inside the mounting box 11 by bolts. One end of a rotating connecting plate 13 is fixed to the output shaft of the driver 12. The other end of the rotating connecting plate 13 is rotatably connected to a sample plate 14. A sample port 15 is opened inside the sample port 14, and a pressure pad 16 is provided inside the sample port 15. A sliding groove 17 is opened inside the cupping machine a. The sample plate 14 is located in the sliding groove 17, and the sample plate 14 slides along the inner wall of the sliding groove 17 under the action of the rotating connecting plate 13.

[0054] The slide groove 17 is provided in two sets, and the two sets of slide groove 17 are arranged opposite to each other, which makes the sliding of the sample plate 14 more stable.

[0055] The connecting plate 13 has an inclined limiting groove in the middle to prevent the sample plate 14 from sliding excessively.

[0056] By turning on the driver 12 via the control panel b, the rotating connecting plate 13 is rotated, thereby pushing the sample plate 14 to move in the slide groove 17. Then, the sample plate 14 is pushed to the platen sample placement end of the cupping machine a, and the platen sample is inserted into the slide groove 17 and into the sample port 15. Then, the platen sample is held in the sample port 15 by the pressure pad 16. Turning on the driver 12 rotates the connecting plate 13, and the sample plate 14 is slid to the left, thus moving the platen sample into the cupping machine a. This achieves automatic positioning and automatic discharge of the sample, further enhancing the automation of the cupping experiment and accelerating the efficiency of subsequent comparative experiments of platen sample.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for testing the brittle fracture property of coated iron plates, characterized in that: include: S1: Use clamps to secure the coated iron plate sample around its perimeter; S2: The coated iron plate sample is pressed into the die head of the driving device to deform the coated iron plate sample until the coated iron cracks; S3: Measure the ratio of the total crack length extending from the iron edge to the membrane at multiple locations of the iron crack; S4: If the ratio of the length of the membrane extending from the iron edge at the iron crack location to the total crack length is greater than or equal to 0.8, the brittle fracture test of the coated iron plate is: unqualified; The length of the iron crack is greater than 5 mm, the die head is hemispherical with a diameter of 18-22 mm, the die head presses into the coated iron at a speed greater than 0.1 mm / s, the area of ​​the coated iron plate sample is larger than the die head, the coated iron plate sample is prepared by hot melting or adhesive bonding, and the thickness of the coated iron film is 12 μm-25 μm.

2. The method for detecting the brittle fracture property of coated iron plates according to claim 1, characterized in that: The driving device is a cupping machine (a).

3. The method for detecting the brittle fracture property of coated iron plates according to claim 2, characterized in that: The cupping machine (a) is equipped with an automatic feeding and positioning structure (1) on the outside of the placement end. The automatic feeding and positioning structure (1) includes a mounting box (11), which is fixed to the side of the cupping machine (a). A driver (12) is installed inside the mounting box (11). A rotating connecting plate (13) is connected to the output shaft of the driver (12). A sample plate (14) is connected to the other end of the rotating connecting plate (13). A sample port (15) is opened inside the sample plate (14). A pressure pad (16) is provided inside the sample port (15). A sliding groove (17) is opened inside the cupping machine (a).

4. The method for detecting the brittle fracture property of coated iron plates according to claim 3, characterized in that: The slide (17) is provided in two sets, and the two sets of slide (17) are arranged opposite to each other.

5. The method for detecting the brittle fracture property of coated iron plates according to claim 3, characterized in that: An inclined limiting groove is provided in the middle of the connecting plate (13).

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