Round pipe processed through tube mill has incomplete roundness and straight rate, so this is the process to correct them.

Straightener roll should be adjusted for left, right, top and bottom in accordance with pipe’s external diameter. When the pipe’s external diameter is small, it has smaller contact degree.

When the pipe’s external diameter is big, contact degree gets bigger. Therefore, line speed is faster as the pipe’s external diameter is smaller, and line speed is slower as the pipe's external diameter is bigger.