Causes and Prevention Methods of Bubble, Peel and Scratch of Aluminium Profiles

Ⅰ. Bubble of aluminium profile

The local skin metal which we called bubble is continuously or discontinuously separated from the base metal, and is manifested as a circular single or strip-shaped cavity raised defect.

(1) The main causes of bubbles

1. When extruding, the extrusion cylinder and extrusion pad have dirt, such as moisture and oil.

2. The air between the worn part and the ingot enters the metal surface during extrusion due to the wear of the extrusion cylinder.

3. There is moisture in the lubricant.

4. The ingot structure itself has loose and porosity defects.

5. The heat treatment temperature is too high, the holding time is too long, and the atmosphere humidity in the furnace is high

6. The hydrogen content in aluminium extruded profiles is too high.

7. Temperature of extrusion cylinder and ingot is too high.

(2) Prevention and control methods

1. Keep the surfaces of tools and ingots clean, smooth and dry.

2. Reasonably design the matching size of the extrusion cylinder and the extrusion gasket, check the size of the tool frequently, repair the extrusion cylinder in time when there is a big belly, and the extrusion gasket should not be out of tolerance.

3. Ensure that the lubricant is clean and dry.

4. Strictly abide by the extrusion process operation process, exhaust in time, cut correctly, and do not apply oil, completely remove residual materials, keep blanks and molds clean and not polluted.

Ⅱ. The peeling of aluminium profile

This is the phenomenon of local separation between the skin metal and the base metal of the aluminium alloy extrusion product.

(1) The main cause of peeling

1. The inner wall of the extrusion cylinder is adhered to the bush formed by the original metal, when the alloy is replaced and extruded, which is not cleaned properly.

2. The extrusion cylinder and the extrusion pad are not properly matched, and the inner wall of the extrusion cylinder is lined with local residual metal.

3. It is extruded by lubricating extrusion cylinder.

4. It's long time to keep metal on the die hole or the working belt of the die.

(2) Prevention and control methods

1. Thoroughly clean the extrusion cylinder when extruding the alloy.

2. Reasonably design the matching size of the extrusion cylinder and the extrusion gasket, check the tool size frequently, and the extrusion gasket cannot be out of tolerance.

3. Clean up the residual metal on the mold in time.

Ⅲ. Scratches of aluminium profile

The single-striped mechanical scars caused by the contact between the sharp objects and the surface of the product during relative sliding are called scratches.

(1) The main cause of scratches

1. Improper assembly of tools, unsmooth guides and worktables, sharp corners or foreign objects, etc.

2. There are metal chips on the mold working belt or the mold working belt is damaged.

3. There are sand or broken metal chips in the lubricating oil.

4. Improper operation during transportation and inappropriate spreader.

(2) Prevention and control methods

1. Check and polish the mold working belt in time.

2. Check the outflow channel of the product, it should be smooth, and the guide path can be properly lubricated.

3. Prevent mechanical rubbing and scratching during handling.