Pinhole is the primary defect of aluminum foil. The original guess, roll, rolling oil, and even dust in the air to reach the size of 6 microns into the roll crack will lead to pinholes, so 6-micron aluminum foil without pinholes is impossible, can only use how much and size to evaluate it. Because of the improvement of aluminum foil rolling conditions, especially dust prevention and rolling oil useful filtration and convenient roll changing system Settings, the number of pinholes in aluminum foil is increasingly dependent on the material metallurgical quality and processing shortcomings, because pinholes are usually the material shortcomings of the drop, it is difficult to find the corresponding with the original defects.
Generally, the pinhole is primarily related to gas content, doping, compounds, and composition segregation.The adoption of useful liquid aluminum purification, filtration, and grain refinement all contribute to pinhole reduction.Of course, the use of alloying and other methods to improve the hardening characteristics of the material is also helpful to reduce pinholes.High quality hot rolled material can produce pinholes of 6 mm aluminum foil under 100 m2.When the cast and rolled products are purified well, the pinhole of 6-micron aluminum foil is less than 200 /㎡.In the aluminum foil rolling process, other elements of pinholes or many, or is disastrous, thousands of pinholes per square meter is not rare.Useful filtering of rolling oil, short term roll replacement and dust control are necessary to cut pinholes in aluminum foil, and the selection of large rolling force, small tension rolling will also help to cut pinholes.
It is the first roll caused by the shortcomings of aluminum foil, into the point, line, surface three.The most obvious features are presented in three cycles.The primary reason for this defect is: improper roller grinding; Foreign material damage roll defects of the material imprinted roll; Roll fatigue; Roll bump, slip, etc.All elements that can constitute the appearance damage of the roll can constitute damage to the rolling of aluminum foil.Because the aluminum foil rolling roller surface smoothness is very high, the subtle uneven luster will affect its appearance.Regular finishing of the rolling mill, maintaining the cleaning of the mill, ensuring the normal operation of the roller cleaner, regular changing of the roll, reasonable grinding, are all basic conditions to ensure the uniform appearance of aluminum foil rolling.
Because the plate shape is severely bad when the aluminum foil is rolled or opened, it will form a wrinkle; its essence is the lack of tension to make the foil flat.For equipment with a tension dimension of 20MPa, the shape of foil shall not be greater than 30I, and when it is greater than 30I, it will inevitably wrinkle.Because the rolling aluminum foil usually receives more tension than the subsequent processing, some in the rolling are just poor shape, including improper roll grinding, roll shape, incoming material poor shape and improper adjustment of the shape.
The bright spot, bright mark and bright spot caused by the improper application of change oil on shuanghe surface are mainly due to the lack of oil film strength of change oil, or uneven roll surface leads to uneven rolling deformation, and the appearance is like hemp skin or foreign body pressing.It is a useful way to deal with this kind of defects to choose reasonable double compound oil, keep the incoming material clean and roll surface even.Of course, changes in the amount of pressure and selection of good aluminum plate is necessary.
Thickness is difficult to control is a feature of aluminum foil rolling, 3 percent of the thickness of the plate may not be difficult to produce, but in aluminum, foil production is very difficult.The reason is that the thickness of thin, other trace conditions can constitute the impact, such as temperature, oil film, oil, and gas concentration.Aluminum foil rolling roll can reach hundreds of thousands of meters, rolling time as long as 10h around, with the time extension, the thickness is very easy to form, and the thickness of the method of adjustment only tension speed.All these elements constitute the aluminum foil rolling thickness control difficult, so, the real control thickness is less than 3%, many conditions to ensure that the difficulty is quite large.
Grease refers to the rolled aluminum foil with the surface of the remaining oil, that is, in addition to the rolling oil film.The oil is usually by the roll neck or mill outlet on, below the swing, splash, drop on the foil surface, and more dirty, messy composition.Oil stains on the surface of aluminum foil are more serious than those on other rolled materials. Firstly, the finished aluminum foil products are mostly used as decoration or packaging materials, which must have a clean appearance.Second, its thickness is thin, in the back annealing easy to form a bubble, and because of the amount of oil in the area to form too much residue and affect the use.Oil pollution defect is an important index to evaluate the quality of the aluminum foil.
Water spots are white spots formed by water droplets on the foil surface before rolling, which will affect the appearance of the foil surface slightly and lead to belt breakage when severe.Water spots are caused by drops of water in the oil or the rolling mill falling on the foil surface.
Vibration mark is the periodic shear wave on the surface of aluminum foil.There are two reasons for the occurrence of vibration mark: one is because of the roller grinding, the cycle in 10~20mm; The other is rolling because of the oil film discontinuous vibration, often in a speed interval, the period of 5~10mm.The bottom cause of vibration mark is the lack of oil film strength, usually can be used to improve the smooth state to eliminate.
When the thickness reaches below 0.015mm, parallel stripes are formed in the longitudinal direction of aluminum foil, commonly known as tension lines.The tension line distance is at the mercy of 5~20 mm, the smaller the tension, the wider the tension line, the more obvious the stripes.When the tension reaches a certain value, the tension line is very small and even invisible.The smaller the thickness of the tension line is more likely; the double rolling tension line is more likely than the sheet.Increasing tension and roll roughness is a useful way to reduce and eliminate tension line.
The slit is a characteristic shortcoming of foil rolling, where the sheets are slit lengthwise, often accompanied by metallic threads.The opening of the bottom is the inlet side discount, often occurs in the center, mainly because to guess the center lose or roll.The severe slit cannot be rolled, and a subtle slit in the future when splitting, which often constitute a lot of waste.
At the moment of rolling, the strip is crushed, the margin is droplet curve, with a certain width, slightly uncrushed, white strip and densely pinholes.The presence of densely perforated pinholes on the front and rear ends of crushed aluminum foil is a prime indication of the airway and other shortcomings.It is very important to choose the material with low gas content as an aluminum blank.
Take-up defects mainly refer to a loose coil or loose outside tight.Because the aluminum foil receives limited tension, it is difficult to roll hard.It is ideal to obtain the inner tight and outer loose coil, and sufficient tension is the condition to form a certain tension gradient.Therefore, the coiling quality ultimately depends on the shape of the plate, loose and tight coil will form transverse edges, and the loose coil will form an ellipse, which will affect the future processing.
Aluminum foil rolling shortcomings of many varieties, but ultimately the main performance is: hole as a feature of pinhole, roll eyes, slit, airway;Oil, uneven luster, vibration mark, tension line, water spots, bright spots characterized by appearance;To influence the plate shape, wrinkling, discounting and improper winding of the post-processing process;Thickness difference characterized by scale, etc.In essence, aluminum foil unique shortcomings only pinhole class, several other shortcomings of the plate are the same, but the performance of different severity or different demand.