Since steel pipe sections must be welded in the field to construct a pipeline, a key design factor is the weldability of pipe. Weldability describes how easily high-quality butt-welding results can be achieved in the field, as well as welding of the longitudinal seam during the pipe manufacturing process. This is important since poor welds result in leaks and the corresponding threats to public safety, and more difficult welding requirements result in additional construction costs. Requirements for weldability will affect the steel plate metallurgy and other manufacturing processes.
In pipeline design, higher-strength steels are often desirable since the pipe wall can be thinner than for lower strength steels, which results in less steel and thus lower pipe costs. But the thinner pipe wall and the more exotic steels used to create high strengths can make field butt welding more difficult. The ease in which high-quality high-speed field welds can be made by the construction crew must be taken into consideration before a specific pipe type is specified by the designer. Thus, more conventional steels are used in most applications to keep construction costs down, even if pipe costs are higher.