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4 common surface stripes of aluminum alloy profiles

4 common surface stripes of aluminum alloy profiles

4 common surface stripes of aluminum alloy profiles



  • There are many types of stripe defects in extruded aluminum profiles, and the forming factors are more complicated. The following are examples of some common striping causes and solutions.

  1. Friction pattern   

   Every time the light die extruded on the machine, the lines do not correspond to each other.

  • Main reason   

  In the extrusion process, the moment the profile flows out of the die hole, it is tightly close to the working belt to form a pair of dry friction pairs in a hot state, and the work belt divides into two zones-adhesion zones and sliding zone. In the adhesion zone, the metal particles subject to at least two forces: friction and shear. When the friction force of the metal particles in the adhesion area is greater than the shear force, the metal particles will adhere to the surface of the working belt in the adhesion area and scratch the surface of the profile to form friction lines.  

  • Solutions 

1. Adjusting the exit angle α of the mold working belt within the range of -1°~-3° can reduce the height of the attachment area of the working belt, reduce the friction in this area, and increase the sliding areas.

2. Carry out effective mold nitriding treatment to keep the surface hardness of the mold above HV900. The vulcanization of the working belt surface can reduce the friction in the adhesion area and reduce the friction line.

 B. Organization stripes   

  • Main reason 

The structure ingot is uneven, the components segregate, there are serious defects under the surface of the ingot, and the uniformity ingot is not treating. The subsequent extrusion process resulted in uneven surface composition of the profile, which caused the profile to be oxidized. The coloring ability is different, and the formation of tissue stripes.  

  • Solution  

1. Reasonably implement the casting process to eliminate or reduce the structure segregation;   

2. Wagon on the surface of the ingot;  

3. Seriously carry out the homogenization of the ingot.

  

 C. Metallic bright pattern   

   In an oxidized white material, the color is bright, and in most cases, the color is flat, the width is variable. In the oxidation color, the stripes are light-colored stripes. 

  • Main reason   

Due to the friction or extreme deformation of the metal flow, the local temperature of the metal will rise very high. Similarly, the uneven metal flow will cause the crystal grains to crack violently and then recrystallize, thereby changing the structure in the subsequent oxidation treatment. In this case, vertical bright streaks will appear on the surface of the contour, and the coloring process will make the contour colorless or show light-colored streaks.

  • Solution  

1. Reasonably design the mold structure;   

2. For mold processing, pay attention to the transition of the working zone to prevent the working zone from falling.

3. Ensure that the old bridge is in the shape of a drop and eliminate edges and corners. 

 

 D. Welding stripes   

The welding stripes (also called weld seams) are straight and very long. They are mostly light gray in oxidized white material, and light in colored material.

  • Main reason

1. The design of the mold diverting hole is too small.

2. The depth of the welding chamber is not enough to ensure sufficient pressure.

3. During the extrusion process, the supply of aluminum in the die welding chamber is insufficient.

4. The extrusion process is unreasonable and improper lubrication.

  • Solution

1. Reasonably design the mold structure.

2. Pay attention to the coordination of extrusion temperature and extrusion speed.

3. Minimize lubrication or non-lubrication.

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