Method for detecting brittle failure of laminated iron plate

Abstract

The invention discloses a method for detecting brittle failure of a laminated iron plate, which comprises the steps of sample preparation, sample cupping processing and sample cupping data analysis, so as to simulate the adhesion condition of a film when iron is cracked at a notch when the laminated iron is used for manufacturing a can / a cover, and judge whether the laminated iron generates a wiredrawing defect in the subsequent can / cover manufacturing process according to the adhesion area of the film, so as to detect the brittle failure of the laminated iron plate. Actual tank / cover making judgment is not needed; according to the method, the semispherical mold is directly pressed into the laminated iron plate until the iron cracks, whether the laminated iron has the defect that the laminated iron is elongated at the notch in the subsequent can / cover making process or not is judged by measuring the ratio of the length of the film extending out of the edge of the iron at the iron crack position to the total crack length, actual can / cover making judgment is not needed, and the working efficiency is greatly improved. And a simple, rapid and reliable detection method is provided for the brittle failure of the laminated iron flat plate sample.

Description

Technical Field

[0001] The present invention relates to the technical field of performance detection of metal packaging materials, and specifically relates to a method for detecting the brittle fracture property of coated iron sheets. Background Art

[0002] Coated iron used in the field of metal packaging is a packaging material composed of a steel plate with a thickness in the range of 0.13 mm - 0.6 mm and a film with a thickness in the range of 12 μm - 25 μm, which combines the dual performance advantages of metal and plastic. Since the plastic film has a higher elongation at break than the coating, the coated iron has good deep drawing performance and is usually used as a substitute for painted iron in metal packaging fields such as food, beverage, and chemical industry.

[0003] Although coated iron products have many performance advantages compared to painted iron, they also bring troubles when applied to can / make lid production. For example, in processes such as stamping and trimming where the coated iron needs to be cut, if the die cutting edge is not sharp, or the die design uses a pulling break rather than a cutting method, it is very easy to cause the situation where the film is stretched and drawn at the iron fracture position. This incomplete fracture of the film of the coated iron will cause the film to remain at the cut position of the can / make lid finished product, affecting the efficiency of making lid / can, damaging the die, and even bringing foreign matter pollution to the contents.

[0004] Currently, national standards such as GB / T 40871-2021 "Plastic Film Thermally Clad Steel Plate and Strip", GB / T 41899-2022 "General Rules for the Quality of Coated Tin or Chromium Plated Thin Steel Sheets for Food Containers", and GB / T 43951-2024 "General Rules for the Quality of Coated Iron and Coated Aluminum for Food Containers" have been successively formulated for the detection and evaluation methods and product standards of metal packaging materials containing coating layers or film layers. However, there is no method in these standards to detect whether the coated iron has such insufficient brittle fracture property. It can only be known through the actual operation of can / make lid manufacturers, which is a post-detection method. By this time, the coated iron has often been mass-produced, which brings great obstacles to the popularization and application of coated iron in the downstream. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for detecting the brittle fracture property of coated iron sheets to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A method for detecting the brittle fracture property of coated iron sheets, including:

[0007] S1: Fix the coated iron flat sample using a fixture;

[0008] S2: Press the die head into the coated iron flat sample through a driving device to deform the coated iron flat sample until the coated iron cracks;

[0009] S3: Measure the ratio of the total crack length of the film extending from the iron edge at the iron crack position;

[0010] S4: When the ratio of the length of the film extending from the iron edge at the iron crack position to the total crack length is greater than or equal to 0.8, the brittle fracture detection of the coated iron sheet is: unqualified;

[0011] Preferably, the length range of the iron crack is above 5 mm.

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

[0013] Preferably, the area of the coated iron flat sample is larger than the die head.

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

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

[0016] Preferably, an automatic feeding and positioning structure is installed outside the placing end of the cupping machine. The automatic feeding and positioning structure includes an installation box fixed to the side of the cupping machine. A driver is installed inside the installation box. A rotating connecting plate is connected to the output shaft of the driver. The other end of the rotating connecting plate is connected to a sample plate. A sample opening is provided inside the sample plate, and a pressure pad is arranged inside the sample opening. A chute is provided inside the cupping machine.

[0017] Preferably, there are two groups of the chutes, and the two groups of chutes are arranged oppositely.

[0018] Preferably, an inclined limiting groove is arranged in the middle of the connecting plate.

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

[0020] By directly pressing a hemispherical mold into the coated iron sheet until the iron cracks, and measuring the ratio of the length of the film extending from the iron edge at the iron crack position to the total crack length to determine whether the coated iron will produce the defect of wire drawing at the cut during the subsequent can-making / cover-making process, without the need to actually make cans / covers for judgment, a simple, fast and reliable detection method for the brittle fracture of the coated iron flat sample is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of the cupping machine of the present invention;

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

[0023] Figure 3 Schematic top cross-sectional structure diagram of the automatic feeding and positioning structure of the present invention;

[0024] Figure 4 Schematic side and top cross-sectional structure diagram of the sample plate of the present invention;

[0025] Figure 5 Schematic structure diagram of the sample port of the present invention;

[0026] Figure 6 Schematic diagram of the unpolished coated iron flat plate sample of the present invention;

[0027] Figure 7 Schematic diagram of the polished coated iron flat plate sample of the present invention.

[0028] In the figure: 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, sliding groove - 17. Detailed implementation manners

[0029] In order to further explain the technical solution of the present invention, the following will be elaborated in detail through specific embodiments.

[0030] The present invention provides a method for detecting the brittle fracture property of coated iron sheets, including: fixing a coated iron flat plate sample with a fixture, pressing a hemispherical die into the coated iron sheet until the iron cracks, the diameter of the hemispherical die is 18 - 22 mm, and the hemispherical die is pressed into the coated iron at a speed greater than 0.1 mm / s by a driving device to cause the coated iron to deform until the iron cracks by more than 5 mm; measuring the ratio of the length of the film extending out of the iron edge at the iron crack position to the total crack length, and of course, the ratio of the area extending out of the iron edge to the total crack area can also be used, which is not limited herein; when the ratio of the length of the film extending out of the iron edge at the iron crack position to the total crack length is greater than or equal to 0.8, the detection of the brittle fracture property of the coated iron sheet is: unqualified;

[0031] The driving device is a cupping machine a, and an automatic feeding and positioning structure 1 is installed outside the placement end of the cupping machine a;

[0032] By directly pressing a hemispherical mold into the coated iron sheet until the iron cracks, and judging whether the coated iron will produce defects such as being stretched at the cut during the subsequent can - making / cover - making process by measuring the ratio of the length of the film extending out of the iron edge at the iron crack position to the total crack length, there is no need to actually make cans / covers for judgment, providing a simple, rapid and reliable detection method for the brittle fracture property of the coated iron flat plate sample;

[0033] Take a flat sample of coated iron with a thickness of 0.28 mm. The A side is coated with a 15-μm polyethylene terephthalate (PET) film, and the B side is coated with a 19-μm PET film. To evaluate the brittle fracture of the coated iron, take a sample of coated iron sheet with a length of 50 mm and a width of 140 mm, clamp it in a fixture, and press it from the A side into the B side with a hemispherical punch with a diameter of 20 mm at a pressing speed of 0.2 mm / s. Stop when the coated iron cracks at the top of the hemisphere and the crack length exceeds 5 mm, and measure the ratio between the length of the film stretched on the iron and the total length of the iron crack.

[0034] Example 1:

[0035] Method for determining whether wire drawing defects will occur during the subsequent pipe making / cover making process of coated iron sheets:

[0036] Take a sample of the flat coated iron plate, cut the flat coated iron plate sample into a circular sample with a diameter of 50 mm, place the test surface on the Erichsen cupping machine a, and set the Erichsen cupping machine a to press into the sample at multiple points at a speed of 0.2 mm / s - 0.8 mm / s. The cupping crack length is 8 - 12 mm, measure r and L, and calculate W:

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

[0038] L = the total length of the iron crack

[0039] W = r / L

[0040] If W ≥ 0.8, it is determined as unqualified.

[0041] Compared with the prior art, the beneficial effect of Example 2 is that by simulating the adhesion of the film at the cut when the iron cracks during the can making / cover making process of coated iron through cupping on a flat plate, and judging whether wire drawing defects will occur during the subsequent can making / cover making process of coated iron by the bonding area of the film, that is, whether the brittle fracture is qualified, without the need to actually make cans / covers for judgment, providing a reliable detection method for the factory inspection of coated iron products.

[0042] Example 2:

[0043] Take a flat sample of coated iron with a thickness of 0.14 mm. The A side is coated with a 19-μm polyethylene terephthalate (PET) film, and the B side is coated with a 12-μm PET film. The sample size is 50 mm in length and 70 mm in width. Clamp it in a fixture, use a hemispherical die with a diameter of 18 mm, and press it from the B side of the sample into the A side at a speed of 0.8 mm / s until the iron deformation crack length reaches 5 mm and then stop. Measure r and L, and calculate W:

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

[0045] L = the total length of the iron crack

[0046] Calculate W = r / L

[0047] If W ≥ 0.8, it is determined as unqualified.

[0048] The problem to be solved in the third embodiment is how to simulate the followability of the film and iron cracking after die stamping during can / mouthpiece making in the state of a coated iron flat sample. Since the film of coated iron usually has a thickness of more than 12 μm to ensure the barrier performance, and the film is tightly attached to the iron surface. When die stamping, the upper and lower dies make relative movements on both sides of the coated iron, causing the iron to be sheared and fractured, and the film fractures along with the iron. At this time, the film will not elongate at the fracture surface of the iron. However, if the cutting edge of a certain tool of the die becomes blunt during long-term use, or the die is severely worn due to long-term use, or the clearance between the upper and lower dies is too large, it will cause the shear clearance between the die and the material to be too wide. The film may elongate along the iron crack under the action of the shear force, resulting in the edge of the film exceeding the edge of the iron and showing the phenomenon of film drawing in the final product. This situation is not allowed in the food packaging field because it will involve foreign matter contamination and also cause great trouble to subsequent processing.

[0049] In the second embodiment, a hemispherical die head is pressed into the coated iron until the iron is deformed and cracked. At this time, the film is not cut by the shear force but torn. In this case, observing the synchronization of the film and iron fracture can reflect the fracture situation of the film under the condition of a dull die during actual stamping. This method is simple and easy to operate, and can effectively reflect the possible situation of coated iron wire drawing during the stamping process in the state of the coated iron being a flat plate.

[0050] In this method, the speed of the cupping is not strictly limited because its purpose is to fracture the iron, but maintaining a uniform speed will make the result judgment more accurate. This method is applicable to the evaluation of various samples of coated iron for current metal packaging.

[0051]

[0052] The above detection method is not limited to coated iron materials based on SR materials and DR materials.

[0053] Please refer to Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5, the present invention provides a method for detecting the brittle fracture property of coated iron sheet, which includes an automatic feeding and positioning structure 1. The automatic feeding and positioning structure 1 includes an installation box 11, which is fixed to the side of the Erichsen machine a. A driver 12 is installed inside the installation box 11 by bolts. One end of the output shaft of the driver 12 is fixed to one end of a rotating connecting plate 13, and the other end of the rotating connecting plate 13 is rotatably connected to a sample plate 14. A sample opening 15 is provided inside the sample plate 14, and a pressure pad 16 is arranged inside the sample opening 15. A sliding groove 17 is provided inside the Erichsen machine a, and 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] Among them, there are two groups of sliding grooves 17 in total, and the two groups of sliding grooves 17 are arranged oppositely, so that the sliding of the sample plate 14 is more stable.

[0055] Among them, an inclined limiting groove is provided in the middle of the connecting plate 13, which can prevent the sample plate 14 from sliding excessively.

[0056] Turn on the driver 12 through the control panel b to make the rotating connecting plate 13 rotate, thereby pushing the sample plate 14 to move in the sliding groove 17, and then push the sample plate 14 to the placing end of the coated iron flat sample of the Erichsen machine a. Insert the coated iron into the sliding groove 17 and then into the sample opening 15, and then clamp the coated iron in the sample opening 15 through the pressure pad 16. Turn on the driver 12 and the rotating connecting plate 13 to slide the sample plate 14 to the left, and move the coated iron flat sample into the Erichsen machine a, so as to realize the automatic positioning and placing of the sample and automatic discharging, further strengthen the automation of the Erichsen test processing, and improve the efficiency of subsequent multiple comparative tests of the coated iron.

[0057] The above are only the preferred examples of the present invention and are not used 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 perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for detecting the brittle fracture of a coated iron plate, characterized in that: include: S1: Use a clamp to fix the coated iron plate sample around; S2: The die head of the driving device is used to press the coated iron flat plate sample into the coated iron flat plate sample to deform the coated iron flat plate sample until the coated iron cracks; S3: Measure the ratio of the total crack length of the film extending out of the iron edge at multiple surface positions of the iron crack; S4: The ratio of the length of the film extending out of the iron edge at the iron crack position to the total crack length is greater than or equal to 0.8, and the brittle fracture test of the coated iron plate is: unqualified.

2. A method for detecting brittle fracture of coated iron sheet according to claim 1, characterized in that: The length of the iron crack is more than 5 mm.

3. The method for detecting brittle fracture of coated iron sheet according to claim 1, characterized in that: The die head is hemispherical, with a diameter of 18-22 mm, and the speed at which the die head presses into the coated iron is greater than 0.1 mm / s.

4. The method for detecting brittle fracture of coated iron sheet according to claim 1, characterized in that: The area of ​​the coated iron flat plate sample is larger than the die head.

5. The method for detecting brittle fracture of coated iron sheet according to claim 1, characterized in that: The coated iron flat plate sample is prepared by a hot melt method or an adhesive method, and the thickness of the coated iron film is 12 μm-25 μm.

6. A method for detecting brittle fracture of coated iron sheet according to claim 5, characterized in that: The driving device is a cupping machine (a).

7. A method for detecting brittle fracture of coated iron sheet according to claim 6, characterized in that: An automatic feeding positioning structure (1) is externally arranged on the placement end of the cupping machine (a), and the automatic feeding positioning structure (1) comprises a mounting box (11), and the mounting box (11) is fixed on the edge of the cupping machine (a). A driver (12) is installed inside the mounting box (11), and a rotating connecting plate (13) is connected to the output shaft of the driver (12), and the other end of the rotating connecting plate (13) is connected to a sample plate (14), and a sample port (15) is provided inside the sample plate (14), and a pressure pad (16) is provided inside the sample port (15), and a slide groove (17) is provided inside the cupping machine (a).

8. A method for detecting brittle fracture of coated iron sheet according to claim 7, characterized in that: The slide grooves (17) are provided in two groups, and the two groups of slide grooves (17) are arranged opposite to each other.

9. A method for detecting brittle fracture of coated iron sheet according to claim 7, characterized in that: An inclined limiting groove is arranged in the middle of the connecting plate (13).

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