Welded steel pipes, also known as seam steel pipes, are generally welded from steel plates or steel strips. According to the surface treatment of the pipe, it is divided into two types: galvanized and non-galvanized. The galvanized surface is white, also called white iron pipe or galvanized steel pipe; the surface without galvanized is ordinary welded steel pipe
, also called black iron pipe. Galvanized welded steel pipes are often used for pipelines that require relatively clean transportation media, such as domestic water, purified air, and instrument air. Non-galvanized welded steel pipes can be used for steam, gas, compressed air, and condensed water.
According to user requirements, welded steel pipes can be divided into two types at the factory, one is pipe end with thread, and the other is pipe end without thread. The length of each welded steel pipe with thread at the pipe end is 4-9m, and the length of each welded steel pipe without thread is 4-12m.
Welded steel pipes are divided into thin-walled steel pipes, thickened steel pipes, and ordinary steel pipes according to different wall thicknesses. Ordinary steel pipe is the most used on the process pipeline, and its test pressure is 2.0MPa. The test pressure of the thick steel pipe is 3.0 MPa.
There are many connection methods for welded steel pipes, including screw connection, flange connection and welding. The flange connection is divided into threaded flange connection and welding flange connection, and the welding method is divided into gas welding and arc welding.
The specifications of commonly used welded steel pipes range from 6 to 150 mm in nominal diameter.