Steel pipes are produced by two distinct methods that would eventually result in either a welded or seamless pipe. In both methods, raw steel is first cast into a more workable starting form. Then it is made into a pipe by stretching the steel out into a seamless tube or forcing the edges together and sealing them with a weld. The first methods for producing steel pipes were introduced in the early 1800s, and they have steadily evolved into the modern processes today.
The amount of carbon that steel contains determines its characteristic. Steel is considered as carbon steel when no minimum content is specified or required for chromium, cobalt, niobium, molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other elements to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.4%; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65%, silicon 0.6%, copper 0.6%. The majority of the steel produced globally falls into the category of carbon steel.
n general, black steel pipes and carbon steel pipes have almost the same procedures for welding. That is in the case of general welding, but not of some specific application like very cold temperatures. Black steel pipe is not really a specification but rather a generic term used primarily by plumbers to distinguish regular steel pipe from galvanized steel pipe.
Black steel pipes are cast from several grades of ductile or malleable iron, whereas carbon steel pipes are generally welded or seamless. Black steel pipes are used for underground or submerged applications as well as for mainstream pipes and branches subjected to acids. It is also common to use cast iron pipes and fittings for municipal cold-water lines 4″ diameter and above. Commercial die casting is unsuitable for lines subjected to expansion strains, contractions, and vibration unless the pipe is very heavy. It is not suitable for superheated steam or for temperatures above 575 degrees F. Cast iron pipes in underground applications (such as sewer lines) usually have bell and spigot ends whereas exposed pipes usually have flanged ends.
