Common defects in welds include porosity, slag inclusion, incomplete penetration, lack of fusion and cracks.

Longitudinal welded pipes are formed by bending steel plates or steel strips and then welding them. According to the weld form, it is divided into straight seam welded pipe and spiral welded pipe.

Generally, according to the different uses and working conditions of the steel pipe, different technical conditions should be proposed for the allowable deviation of the steel pipe size, surface quality, chemical composition, mechanical properties, process performance and other special properties.

The data of Brinell hardness measurement is accurate and stable, and it is suitable for detecting unquenched seamless steel pipes, cast iron steel pipes, non-ferrous metals or light and soft bearing alloy steel pipes.

Cold rolled seamless steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, and other steel pipes, as well as carbon thin-walled steel pipes and alloy thin-walled steel pipes.

The strength of thick-walled spiral steel pipes is generally higher than that of large-diameter straight seam steel pipes.