+86 371 65621391

Product knowledge

Aluminum foil 12 major defects

addtiame:2016/10/18 click:
Aluminum foil has superior function of blocking air, anti-oxidation, waterproof, moisture-proof; High resistance function of blasting, puncture resistance tearing resistance function is strong; High temperature resistant, low temperature resistant, oil resistant, the function is good; Avirulent insipidity, accord with food, medicine packaging health scale; Good heat sealing function, good flexibility, high barrier function. What, then, the shortcomings of aluminium?
(1) the pinhole. Pinhole is the main defect of aluminum foil material. Raw material, roll on, rolling oil, the size of the dust in the air even reached about 6 microns into the roll gap will cause pinhole, so there was no 6 microns aluminum foil pinhole is impossible, can only use many size and evaluate it. Due to the improvement of aluminum foil rolling conditions, especially the dust and rolling oil filter effectively and convenient roll changing system Settings, aluminum foil pinhole number more and more dependent on the metallurgy quality and the processing defects of raw material, due to the shedding of pinhole tend to be raw material defect, it is difficult to find the corresponding relationship with the original defects. It is generally believed, pinhole and air content and composition segregation, inclusion, compounds. Take effective liquid aluminum purification, filtration, pinhole grain refinement are reduced. , of course, use the method to improve such as alloying material hardening characteristics can also help reduce pinhole. High quality hot rolling material 6 microns of rolling aluminum foil pinhole can be below 100 / ㎡. Roll material when good purification, 6 microns aluminum foil pinhole under 200 / ㎡. In the process of rolling aluminum foil, many other factors that cause the pinhole, even disastrous, it isn't unusual to thousands of pinhole per square metre. Rolling oil filter effectively, roll short-term replacement and dust prevention measures are necessary conditions under which is to reduce the aluminum foil pinhole, and adopted the rolling force, small tension rolling will also help reduce the pinhole.
(2) roller, roller eye, uneven luster. It is mainly caused by the roll aluminum foil defects, is divided into three of dot, line, face. The most distinguishing feature of three cycles. The main cause of this defect is: the roll is not the correct grinding; Foreign objects damage roll: incoming defect printing roll; Roll fatigue; Collision between roller, skid, etc. All the possible factors of the surface damage of the roll, all can harm on the formation of rolling aluminum foil. Because of the high aluminum foil rolling roller surface roughness, mild luster uneven may also affect its surface state. Regular cleaning mill, maintain the cleanness of rolling mill, the normal work of the roller clearer, roll change regularly, reasonable grinding, after all is to ensure that the aluminum foil rolling surface uniform basic conditions.
(3) the wrinkles. Due to the strip shape serious adverse, will be formed in aluminum foil coiling or buckling, its essence is tension is not enough to make the foil surface flattening. For liwei zhang 20 mpa device, on the surface of the foil flatness shall not be greater than 30 I, when more than 30 I will wrinkle. Because of rolling aluminum foil often bear the tension of greater than the subsequent processing, some just show the flatness bad when rolling, including roll grinding is not correct, roll shape is wrong, the incoming material and adjusting flatness bad profile is not correct.
(4) the window, bright, bright spot. Receives due to improper use receives oil window, bright speck, bright spot, mainly because receives the oil film strength is insufficient, or roll rolling uneven deformation caused by the uneven surface, appearance is hemp skin or foreign body into shape. Choose reasonable receives oil, keep the material clean and uniform roll roll surface is an effective measure to solve this kind of defect. Of course quantity change and choice of fine aluminum plate is necessary.
(5) thickness difference. Thickness difference is difficult to control is a characteristic of rolling aluminum foil, 3% of the thickness difference in plate production maybe is not difficult, but it's very difficult when aluminum foil production. The reason is that the thickness of thin, all can affect other trace conditions, such as temperature, concentration of oil film, oil and gas, etc. A roll of up to hundreds of thousands of meters of rolling aluminum foil, rolling time for around 10 h, the thickness difference is easy to form, with the extension of time and the means to adjust the thickness is only tension speed. These factors have caused the aluminum foil rolling thickness control is difficult, so the real control thickness difference within 3%, need many conditions to ensure that, difficulty is quite large
(6) oil. The surfaces of the oil pollution is refers to the rolling aluminum foil after redundant oil, namely, except the oil film of rolling oil. These oils are often by roll neck or on the mill outlet, bottom left, splash, drop on the foil, and more dirty, complicated composition. Aluminum foil surface with oil pollution does more harm than other rolling material with greasy dirt, one is due to the aluminum foil products most as a decoration or packaging material, there must be a clean surface; Second, its thickness thin, easy to form the last way annealing bubble, and because more oil in the formation of excessive residue and effect to use. How much oil defects is to evaluate the quality of the aluminum foil a very important indicator.
(7) water spots. Water pollution refers to have water droplets on the foil before rolling, rolling after the formation of the white patches, mild will affect the foil surface condition, serious can cause broken belt. Water pollution is due to the water or oil mill with water droplets formed on the surface of the foil, control of water and water in the oil is the only measures to avoid water spots.
Mark of vibration (8). Periodic vibration mark refers to the aluminum foil surface transverse wave. Cause vibration mark has two kinds: one kind is due to the roll grinding formed when, cycle around 10 ~ 20 mm; The other is a vibration due to oil film when the discontinuity of rolling, often produced in a speed range, cycle for 5 ~ 10 mm. The root cause of the vibration mark is oil film strength is insufficient, can often improve the lubrication condition is used to eliminate.
(9) tension line. When the thickness is 0.015 mm, longitudinal aluminum foil in horizontal stripes, commonly known as the tension of the line. Tension in 5 ~ 20 mm spacing between left and right sides, Zhang Liyu is small, the more tension line width, the more visible stripes. When tension reaches a certain value, the tension of the line is very mild or even disappear. The smaller the thickness of the probability of tension line is larger, the probability of tension line receives rolling a single big. To increase tension and roll roughness is an effective measure to reduce and eliminate tension line, and large tension must be based on good flatness.
Slit (10). Slit is a peculiar defects, foil rolling along the longitudinal straight crack when rolling, often accompanied by metal thread. Slit is the root cause of the entry side discounts, often occur in the middle, mainly due to poor incoming middle loose or roll. Serious slit rolling, and a slight slotted in after cutting split, it often causes a lot of waste.
Airway (11). Strip in rolling time break crushed, a droplet shape curve, rim has certain width, mild airway without crushing, with a white strip with dense pinhole. In the crush of aluminum foil pinhole in the end there is before and after judgment, the prime symbol for the airway and other defects. Airway is derived from the raw material, low air content of materials as aluminum casting is very important.
(12) winding defects. Coiling defect is mainly refers to the volume inside or outside come loose tight. Due to the limited aluminum foil on the tension, take-up hard roll is difficult. Exterior made in volume is optimal, and enough tension is to form a certain tension gradient condition. So, coiling quality ultimately depends on the strip shape quality, roll forming loose outside close in horizontal edge, while loose volume will form the ellipse, it will affect after processing.
Although many defects of rolling aluminum foil sort, but in the end, main show is: roll is characterized by the hole of the pinhole, eye, slotted, airway; Oil is characterized by surface condition, uneven luster, vibration mark, tension line, water spots, highlight bright spot; To influence after the process of strip shape, wrinkling, discounts, coiling bad; Characterized by the size of thickness etc. In essence, the aluminum foil only pinhole defect category, plate also has several other defects, only the performance of different severity or different requirements.