How To Avoid Stripes On Aluminum Tubes?

The striations on the outside of extruded aluminum tubes are so pronounced after anodization that it is hard not to notice them, and customers can be forgiven for not buying them. 

Therefore, any aluminum pipe manufacturers should figure out why extruded aluminum tubes surface stripes exist, and how to solve this problem.

Here is the content list:

• What Are Kinds Of Stripes Of Aluminum Tubes?

• Why Are There Stripes On Surface Of Aluminum Tubes?

• How To Avoid Strips On Aluminum Tubes?

What Are Kinds Of Stripes Of Aluminum Tubes?

• Work tape striations

It causes the surface of the extruded aluminum tubing to appear as if a needle were used to draw a number of thin, continuous lines parallel to the extruding direction.

When the light is reflected off the surface of the untreated aluminum tube, a continuous "extrusion line", "hot line" or "shadow" appears. As you look at the surface of the aluminum tube from different angles, these "lines" will appear and disappear randomly.

It is not caused by the working surface of the mold, generally because the whole working belt of the mold is not flat and inclined or concave, resulting in unstable coating and uneven flow of the working belt. In addition, the sharp angle of change of the working belt can also cause this striation on aluminum pipe surface, which is caused by uneven metal flow velocity or insufficient supply. Bad working with rounded edge can cause the profile surface to produce striations on a wide plane.

• Tissue striations

The "tissue striation" mostly appears in the thickness variation part of aluminum pipe, which can be determined by the corrosion active anodic oxidation treatment. When the corrosion temperature is changed, the striations either disappear or their width and shape change.

• Oxide striation

It is difficult to distinguish the oxide stripes on the surface of the aluminum tube. After corrosion or anodic oxidation treatment, it is easy to identify the defective parts due to the disappear of formation of oxide film.

Why Are There Stripes On Surface Of Aluminum Tubes?

This defect is mostly found in the parts with large wall thickness difference of aluminum tube, the welding part of metal under the splitter bridge and the back side with "branch" on the inside and threaded holes. Before dealing with the striation marks on the surface of the aluminum tube, we need to figure out what is the cause of the stripes.

• Metal flow

The "branches" and threaded holes on the inner side of the aluminum tube cause surface striations due to insufficient or excessive metal flow supply.

• Weld area

Aluminum tube surface streaks are caused by welding zone under die splitter bridge.

• Design problems

There are some problems in the design of aluminum tube section. Because of the Great Wall thickness difference of aluminum tube, the striation of working strip length will occur after anodization.

• Cooling capacity

Because the cooling capacity of the machine is not enough, which results in black mottled area after anodization on aluminum pipe.

• Bar Quality

The quality of the billet itself is bad, which affects the aberration of the stripes after the extrusion aluminum pipe is anodized.

 How To Avoid Strips On Aluminum Tubes?

1.        Check the customer's drawing of aluminum pipe, whether there are problems such as large wall thickness difference, branch and thread hole in the decorative surface of aluminum tube.

2.        While ensuring the strength of the die, the welding chamber should be as large as possible so that the metal can form enough hydrostatic pressure.

3.        For large diameter aluminum tubes or large size hollow aluminum tubes, the upper welding chamber may be provided on the mold.

4.        Sometimes the striations are formed by the cast billet itself, and the production of seamless aluminum tubes requires the billet to be heated at a uniform temperature and annealed thoroughly.

5.        After extrusion die hole, the grain size depends on the temperature into the quenching zone and the cooling rate in the quenching zone. If the cooling temperature is too low and the cooling speed is not uniform, the grain size will be too large or uneven, so that the color difference of seamless aluminum tube will be more obvious after anodization, which requires the operator to timely adjust the size of the cooling system wind pressure and cooling water pressure.

How to prevent the surface of aluminum tube occurring stripes, I believe you have the answer. We recommend you to cooperate with us rather than manufacture aluminum tubes by yourself. We are one of the best aluminum tube manufacturers in China. We sincerely serve you. If you are a seller, we will particularly welcome you to contact us.