What is the defect in outer surface of the hot expanded seamless pipe?

The difference between high frequency welded steel pipe and straight-seam welded steel pipeFirst. Different in natureA. High-frequency welded steel pipe: After the hot-rolled coil is formed by the forming machine, the skin effect and proximity effect of the high-frequency current are used to heat an

Usage and functions of large-diameter straight seam welded pipes1. The use of large-diameter longitudinally welded pipes can be divided into oil well pipes (casings, tubing, and drill pipes, etc.), line pipes, boiler pipes, mechanical structure pipes, hydraulic prop pipes, gas cylinder pipes, geolog

Classification of pipe pilesPipe piles are divided into post-tensioned pre-stressed pipe piles and pre-tensioned pre-stressed pipe piles, pre-stressed concrete pipe piles (PC pipe piles), and pre-stressed concrete thin-walled pipe piles (PTC pipe piles), and high-strength pre-stressed concrete pipes