The steel tube has the seamless type and welded type (seam type). In terms of the section shape, it can also be divided into the circular type and irregular type. The extensively used type is circular steel pipe. In some areas, the irregular steel type is also employed, including square type, rectangular type, semicircular type, hexagonal type, equilateral triangle type, octagon type, and more.
The steel tube that bears fluid pressure should take the hydrostatic test to inspect the ability of withstanding pressure and quality. If there is no leakage, wetting or expansion coming out under the required pressure, we can say that the steel pipe is qualified. Some of the steel pipe should go through the edge curling test, flaring test, flattening test, etc. according to the standard or the demands of the customers.
The welded steel tube is produced by using the steel plate or steel strip through bending forming and welding. It falls into the longitudinal type and spiral type in line with the welding seam form. By purpose, the welded steel pipe has the ordinary type, galvanized type, oxygen blowing type, spiral type, metric type, welding thin-walled type, welding irregular type, electric wire conduit, roller pipe, as well as the type for deep well pump, automobile, transformer, etc.