... , square, rectangle pipe.its Thickness from 0.6mm up to7.0mm. High-frequency welded pipe line Name & Feature:High-frequency welded pipe/tube line; High frequency welded pipe/tube making machine; welding machine ... . 4. Higher safety for operation.Process for making industrial pipe :strip unfolding, forming, welding, inside polishing, grinding, rough sizing, bright annealing, precise ...