There is graphite or bubbles on the inner surface of the aluminum tube

Graphite is pressed into the inner surface of the aluminum tube because there is too much solid lubricant in the lubricant.

The graphite lumps accumulated on the extrusion needle were not cleaned off in time.

The finish of the inner surface of the aluminum billet is too poor.

The graphite quality is not good enough, there is too much ash and impurities, and the particle size is too large, so the impurities need to be removed.

There are scratches or bubbles on the inner surface of the aluminum tube. Is it because the extrusion needle is scratched and has sharp edges? Does the extrusion needle need to be repaired?

There is moisture, sand, metal chips in the lubricant, and impurities need to be removed.

The reason why there are water mark-like scratches on the inner surface of the aluminum tube is that the grooves machined on the inner surface of the ingot are too deep and need to be adjusted.