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The main defects of aluminum foil

The main defects of aluminum foil

  • Release date:2020-03-28
  • Summary: 1. Pinhole: The main defect of pinhole three aluminum foil. In the raw materials, on the rolls, in the rolling oil, and even when the size of the dust in the a

     1. Pinhole: The main defect of pinhole three aluminum foil. In the raw materials, on the rolls, in the rolling oil, and even when the size of the dust in the air reaches about 6 m, entering the roll gap will cause pin holes. Therefore, 6 μm aluminum foil is not possible without pin holes. It can only be evaluated by how many and the size. Due to the improvement of aluminum foil rolling conditions, especially the effective filtering of dust and rolling oil and the setting of a convenient roll changing system, the number of pinholes in aluminum foil increasingly depends on the metallurgical quality and processing defects of the raw materials. It is difficult to find the corresponding relationship with the original defect when the raw material defect falls off. It is generally believed that pinholes are mainly related to gas content, inclusions, segregation of compounds and components. Effective aluminum purification, filtration, and grain refinement all help reduce pinholes. Of course, the use of alloying and other means to improve the hardening characteristics of the material also helps reduce pinholes. High-quality hot-rolled rolled 6μm aluminum foil pinholes can be less than 100 per square meter. When the cast material is better cleaned, the 6μm aluminum foil pinholes are less than 200 per square meter. During the aluminum foil rolling process, there are many other factors that cause pinholes, even catastrophic. It is not unusual to have thousands of pinholes per square meter. Effective filtering of rolling oil, short-term replacement of rolls and dust-proof measures are all necessary conditions to reduce pinholes in aluminum foil. Using large rolling forces and small tension rolling will also help reduce pinholes.

    2. Roll marks, roll eyes, and uneven gloss: It is mainly aluminum foil defects caused by rolls, which are divided into three types: dots, lines, and surfaces. The most significant feature appears in three cycles. The main causes of such defects are: incorrect grinding of the rolls; foreign objects damage to the rolls: incoming defects print and damage the rolls; roll fatigue; collision between rolls, slipping, etc. All factors that can cause damage to the surface of the roll can pose a hazard to aluminum foil rolling. Because the surface of aluminum foil rolling rolls is very high, slight uneven gloss will also affect its surface condition. Regular cleaning of the mill, keeping the mill clean, ensuring the normal operation of the roll cleaner, regular roll changes, and reasonable grinding are all basic conditions to ensure that the surface of the aluminum foil after rolling is uniform.
    3. Wrinkling: Due to the bad shape of the plate, wrinkles will be formed when the aluminum foil is coiled or unrolled. The essence is that the tension is not enough to flatten the foil surface. For a device with a tension dimension of 20 MPa, the plate shape of the foil surface must not be greater than 30I, and when it is greater than 30I, wrinkling is bound to occur. Because aluminum foil tends to bear greater tension than subsequent processing during rolling, some only show poor shape during rolling, including incorrect grinding of rolls, incorrect roll shape, bad shape of incoming material, and incorrect adjustment of shape.
    4. Bright spots, bright marks, bright spots: Bright spots, bright spots, bright spots caused by improper use of double oils on double-sided surfaces, mainly due to insufficient oil film strength of double-sided oil, or uneven rolling deformation caused by uneven roller surfaces , Appearance was linen or foreign matter pressed in. Selecting a reasonable double oil, keeping the incoming materials clean and the roll surface uniform is an effective measure to solve such defects. Of course, it is also necessary to change the reduction amount and select the excellent aluminum plate.
    5. Thickness: It is a feature of aluminum foil rolling that it is difficult to control the thickness difference. The thickness difference of 3% may not be difficult in the production of sheet materials, but it is very difficult in the production of aluminum foil. The reason is that the thickness is thin, and other trace conditions can affect the temperature, oil film, and oil and gas concentration. A roll of aluminum foil can reach hundreds of thousands of meters, and the rolling time is about 10 hours. With time, the thickness difference is easy to form, and the only means for adjusting the thickness is the tension speed. These factors all make it difficult to control the thickness of aluminum foil rolling. Therefore, to really control the thickness difference within 3%, many conditions are needed to ensure that it is quite difficult.
    6. Oil pollution: Oil pollution refers to the excess oil on the surface of the aluminum foil after rolling, that is, oil other than the rolled oil film. These oils are often thrown, splashed, and dripped on the foil surface from the top and bottom of the roll neck or the mill exit, and they are dirty and have complex components. Oil stains on the surface of aluminum foil are more harmful than oil stains on other rolled materials. First, most aluminum foil products are used as decoration or packaging materials, and they must have a clean surface; And because of the large amount of oil, excessive residues are formed there, which affects the use. The degree of oil pollution is an important index for evaluating the quality of aluminum foil.
    7. Water spot: Water spot refers to the white spots formed on the foil surface before rolling, and the white spots formed after rolling will affect the surface condition of the foil when it is mild, and it will cause broken bands when it is serious. Water spots are formed due to water drops in the oil or water drops in the rolling mill. The control of moisture and water in the oil is the only measure to avoid water spots.
    8. Vibration marks: Vibration marks refer to periodic transverse waves on the surface of aluminum foil. There are two causes of vibration marks: one is caused by roller grinding with a period of about 10 to 20 mm; the other is due to the discontinuous vibration of the oil film during rolling, which often occurs in a speed interval with a period of 5 ~ 10mm. The root cause of vibration marks is insufficient oil film strength, which can usually be eliminated by improving the lubrication state.
    9. Tension line: When the thickness reaches below 0.015mm, parallel stripes are formed in the longitudinal direction of the aluminum foil, commonly known as the tension line. The distance between the tension lines is about 5-20 mm. The smaller the tension, the wider the tension lines, and the more obvious the stripes. When the tension reaches a certain value, the tension line is slight or even disappears. The smaller the thickness, the more likely it is to generate tension lines, and the more likely it is to produce tension lines in double-rolling than in a single sheet. Increasing tension and roll roughness is an effective measure to reduce and eliminate tension lines, and large tension must be based on good plate shape.
    10. Slotting: Slotting is a peculiar defect of foil rolling. It cracks straight in the longitudinal direction during rolling, often accompanied by wire. The root cause of slitting is a discount on the inlet side, which often occurs in the middle, mainly due to looseness in the incoming material or poor rolls. Severe seams cannot be rolled, and slight seams are cracked during subsequent slitting, which often results in a large amount of scrap.
    11. Airway: Strip crushing occurs at the break of rolling time, and the edge is a drop-shaped curve with a certain width. The mild airway is not crushed, and it is a white strip with dense pinholes. The presence of dense pinholes at the front and rear of the crushed aluminum foil is the main indicator of airway and other defects. The air duct is derived from raw materials. It is very important to choose a material with low gas content as the aluminum blank.
    12, coiling defects: coiling defects mainly refers to loose coils or tight inside. Due to the limited tension with which aluminum foil is subjected, it is difficult to wind up hard rolls. It is ideal to obtain an inner tight outer loose roll, and sufficient tension is a condition to form a certain tension gradient. Therefore, the quality of the coiling ultimately depends on the shape of the plate. The inner and outer tight coils will form transverse edges, while the loose coils will form ovals, which will affect later processing.
    Although there are many types of aluminum foil rolling defects, the main manifestations are: pinholes, roll holes, slits, and air channels characterized by holes; oil stains, uneven gloss, vibration marks, tension lines, and water characterized by surface conditions. Streaks and bright spots; To affect the shape, wrinkling, discounting, and poor winding of the post-processing; thickness differences characterized by size. In fact, the unique defects of aluminum foil are only pinholes, and other kinds of defective plates also have the same, but the performance is different according to different requirements.

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