https://www.bkneddy.com/ultrasonic-testing-equipment/steel-pipe-testing/ Steel having a hollow section that is much longer than the diameter or circumference. According to the cross-sectional shape, it is divided into round, square, rectangular and special-shaped steel pipes; it is divided into carbon structural steel pipe, low-alloy structural steel pipe, alloy steel pipe and composite steel pipe according to the material; it is divided into conveying pipeline and engineering structure according to the purpose. For thermal equipment, petrochemical industry, machinery manufacturing, geological drilling, steel pipes for high-pressure equipment, etc.; according to the production process, it is divided into seamless steel pipes and welded steel pipes, of which seamless steel pipes are divided into hot rolling and cold rolling (pulling). Two kinds of welded steel pipes are divided into straight seam welded steel pipes and spiral seam welded steel pipe testing.